SMAIL(5)

NAME
/var/lib/smail/* - configuration files used by smail

SYNOPSIS
/var/lib/smail/config
/var/lib/smail/qualify
/var/lib/smail/directors
/var/lib/smail/routers
/var/lib/smail/transports
/var/lib/smail/retry
/var/lib/smail/methods/

DESCRIPTION
The config, qualify, directors, routers, transports, and retry files describe the rules used by smail(8) in processing and delivering mail. In addition to these configuration files, method files may be pointed to by entries in the routers file. The actual paths may differ from system to system and, in addition, the paths to these files, with the exception of the config file itself, may be changed in the config file.

Smail is compiled with a default configuration. This default configuration is suitable for many sites that communicate to other systems via UUCP, or SMTP. For such sites, no configuration files are needed, though it may still be convenient to have a config file for attributes (described below) such as smart_user and smart_path. See the section DEFAULT CONFIGURATION for more details.

COMMON FORMAT CONVENTIONS
In all files used by smail, entries begin with a character in column 1 that is not white space or the character `#'. Entries continue until the next line which begins with a character other than white-space or the character `#', or until the end of the file is encountered.

Comments begin with the character `#', in any column and end at the next newline. A `#' in the first column does not signify the end of an entry.

Variable and attribute names in configuration files are formed of characters from the set of letters, numbers and the character `_'.

String values may be enclosed in double quotes, in which case backslash escapes are processed as in C. If string values are not enclosed in double quotes, the values are limited to characters from the set of letters, digits and the characters ! @ $ % ^ & * - _ + ~ / ? | < > : [ ] { } . ' and `.

Numbers are as in C, with a prefix of 0 specifying an octal constant and a prefix of 0x specifying a hexadecimal constant. In addition, a suffix of k or K specifies a multiplier of 1024 and a suffix of m or M specifies a multipler of 1048576, or 1024K.

String Expansion
Some string values will be variable and filename expanded before being used. When this is done, certain substrings, beginning with $, will be replaced by the value of a smail variable. The names of expansion variables are either a single character, or are multiple characters from the set of letters, digits and underscore. A variable name can also be enclosed between { and }, to isolate the variable name from the surrounding text.

In addition to variables, a number of meta-expansions can be used. These expansions are of the form:
    ${meta_name:name}
where meta_name defines some operation to perform on the value of the variable name. Multiple meta-expansions can be specified, and they are processed from right to left. For example:
    ${lc:strip:user}
This strips quotes from the value of the variable user and then converts characters to lower case.

When a string to be expanded begins with the character `~', a home directory is substituted. If only `~' is given, or `~/' is given, then the home directory associated with an address is substituted. If the form ``~username'' is given, where username is the name of a user on the local host, that user's home directory is substituted.

  Conditionals
Conditionals can be used to include text based on whether or not a particular value is non-empty. Conditionals are of the form:
    ${if condition [:]string}
or
    ${if condition {string1} {string2}}
The first form includes string if the condition is true. The second form includes string1 if the condition is true, or string2 if the condition is false. For readability, else can be inserted before the else clause.

Possible conditions are:

!condition
    Negate the truth value of condition.

def:variable
    True if the given expansion variable is defined and is non-empty.

header:header
    True if the message contains a header field named header.

origin:local
    True if the message originated locally.

origin:remote
    True if the message was received from a remote machine.

dest:local
    True if the message is being delivered to an address on the local host.

dest:remote
    True if the message is being delivered to a remote host.

xform:transformation
    True if the transformation being applied to the message, for delivery by the assigned transport, matches the given type. Valid types are: local, inet, uucp, or none.

eq{variable}{string}
    True if the given expansion variable matches the given string.

or{{condition}...}
    True if any of the given conditions are true.

and{{condition}...}
    True if all of the given conditions are true.

  File lookups
String expansions can use lookup procedures to convert a key, taken from a an expansion variable, into a string found in a file or other accessible database. These expansions are defined using the form:
    ${lookup:variable:proto{file-expansion} [:]found-string}
or
    ${lookup:variable:proto{file-expansion}
        {found-string} {not-found-string}
Lookups operate by taking the value of the indicated variable as a key for lookup in a file. The proto string defines how the lookup is to be performed, and file-expansion is a string defining the file or database to search. If the key is found, then the found-string is expanded, otherwise the not-found-string is expanded. A $value reference in found-string is replaced by the value found by the lookup. For readability, then can be inserted before the found clause, and else can be inserted before the not-found clause.

Allowed lookup methods are:

bsearch
    Use a binary search to locate the key in a sorted file, organized as lines beginning with a key separated from a value by blanks.

lsearch
    Use a linear search to locate the key in a plain file, again organized as lines beginning with a key separated from a value by blanks. Comments in this file begin with # and continue until end-of-line. Blank lines are ignored.

dbm Lookup the dbm in a dbm database.

yp  Lookup the key in a remote Sun NIS database.

aliasyp
    Lookup the key in a remote Sun NIS database. This differs from yp in that a nul byte is added to the key before lookup.

nialias
    Lookup the key in a NeXT netinfo database.

  Expansion variables
The complete set of variable names depends upon context, but the following are always available:

bat a string defining a string of characters which identifies where your smail sources originated. See the source file src/version.c for more information.

compile_date or ld_date
    the date when the current smail binary was compiled.

compile_num or ld_num
    a decimal number giving the number of times smail has been compiled since the creation of the source file ldinfo.c.

ctime
    the date and time, in the form returned by the ctime(3) function.

date
    The date and time in ARPAnet format.

spool_date
    The date and time that the message was received by the local host, in ARPAnet format.

grade
    The priority character for the current message. See the grades attribute in the config file for more information on this value.

message_id or id
    the message ID for the current message.

message_size or size
    the total size of the spooled message.

message_body_size or body_size
    the size of the body of the message, which excludes the message header fields, and also excludes any overhead within the message spool file.

patch_number or patch
    the patch level of the smail sources, from the source file patchnum, which contains the date that the most recently applied patch was created, and the number of that patch.

patch_date
    The date when the most recently applied patch was created.

pid or $
    the current process ID.

primary_name or primary
    the canonical name for the local host.

release_date or release
    the release date of the smail sources.

sender or from
    the address of the sender of a message.

sender_name or fullname
    the full-name of the sender, taken either from the -F argument to smail or from the password file.

sender_host
    the sending host, if one is known. This is set automatically for mail received via UUCP or SMTP. It can also be set with -oMs from the command line.

sender_proto
    the sending protocol (e.g. smtp or uucp), if one is known. This is set automatically for mail received via UUCP or SMTP. It can also be set with -oMs from the command line.

sender_program
    The program that queued the message. For mail received via UUCP, this will be, typically, rmail. Otherwise, the sender program will likely by set to sendmail or smail, depending upon the program that typically is invoked for receiving mail.

uucp_name
    the UUCP-network name for the local host.

version
    a short version string for smail.

version_string
    a verbose version string.

visible_name or name
    the local host name used in outgoing addresses.

smail_lib_dir or lib_dir
    the value of the config file variable smail_lib_dir, which is the directory in which configuration files are found.

In addition, the following variables are defined if they are available in the current context:

HOME or home
    the home directory of a user associated with an address.

host
    the remote host string associated with a remote address.

user or addr
    a user name or remaining address string associated with an address.

input_addr
    The address specified in the message, or in an alias or mailing list expansion, that is being processed.

director
    The name of the director that matched the address, if appropriate.

router
    The name of the router that matched the address, if appropriate.

transport
    The name of the transport to be used for delivering to the address, if the address has been successfully resolved.

The following meta-expansions also exist:

lc  convert to lower case.

parent
    interpret the value within the context of the parent local address that produced the associated address. This is useful when the local address that produced an address is desired. Expansion fails if no parent exists.

quote
    enclose the value in quotes, if it would not otherwise be a valid local-form address, within the rules of RFC822. Uses backslash escapes as appropriate. (This is not available in the Alpha release of smail).

strip
    Remove backslashes and double quotes from a value. If a double-quote is preceded by a backslash, the backslash is removed, but the double quote is not. Sequences of whitespace characters and dots are converted to exactly one dot character.

top interpret the value within the context of the original address, supplied to the mailer, that produced the associated address.

uc  convert to upper case.

The following are sample expansions:
	/usr/spool/mail/${lc:user}
with a $user value of ``Tron'' will become:
	/usr/spool/mail/tron
whereas:
    	Received: by $primary_name ($version_string)
		id <$message_id@primary_name>;
		$spool_date
will become something such as:
    	Received: by futatsu.uts.amdahl.com (smail 3.0.2 03-dec-87)
		id <m0c87zK-007zXpC@futatsu.uts.amdahl.com>;
		Tue,  8 Dec 87 19:45 PST
and:
    	$host!rmail ${strip:addr}
with an $addr value of ``Ronald S. Karr'' and a $host value of ``amdahl'' will become:
    	amdahl!rmail Ronald.S.Karr
If a value does not exist (such as $HOME being used when no associated home directory is known, or when a string begins with "~username" and the username is not known, or when $host is used for a local address) then the expansion fails.

THE CONFIG FILE
The config file defines values for global variables used by smail. Each entry in this file gives the name of a variable to be set and defines a string, numeric or boolean value to give to that variable. The recognized forms for entries in the config file are:
    variable_name = string or number variable_name or +variable_name -variable_name
The first form above sets the variable to a string or numeric value, the second form sets a boolean variable, and the last form resets a boolean variable, clears a string value or sets a numeric value to zero.

The following config file specifies a spool file mode of 0400, a maximum message size of 200K, a method directory of /usr/lib/smail/method and disables use of a transport configuration:
    # don't allow others to read spool files
    spool_mode = 0400
    # truncate messages that are too large
    max_message_size = 200k
    # method files are stored in this directory
    method_dir = /usr/lib/smail/method
    # we are using the built in transport definitions,
    # so don't bother looking for a transport file
    -transport_file
The complete list of recognized attributes is given in the following table, in alphabetic order. Note that the default values can be changed when compiling the smail program.
A colon-separated list of domain names for which this host is considered authoritative. A host that is authoritative for a domain has access to all routing information needed for that domain. The primary purpose of this variable is to list domains that will not be matched by the smarthost router driver. If set, then any directories required for spooling and logging will be created if they do not exist. Smail will never try to create required parent directories. When directories are created automatically by smail, they are created with this permission mode mask. See stat(2) for information on what this mode represents. The file name for the console device. This filename is used as a last resort in attempting to write panic messages. The pathname to the COPYING file, which describes your distribution rights and details the warranty information from the authors of smail. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. This string will be expanded to form the Date: header field. This will be used if such a field does not already exist in the header. The default mode of delivery for new mail. This can be one of the values ``foreground'' (immediate delivery in the process that received the message), ``background'' (immediate delivery in a child process, where the process that received the message exits immediately), or ``queued'' (do not attempt delivery until a later queue run). Names the file containing the director configuration information. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. Copy the postmaster on all error messages. Normally only errors that appear to be a result of administrator errors will be mailed to the postmaster. If error_copy_postmaster is set, then errors that are returned to the sender, or that are mailed to owners of mailing lists, will also be sent to the postmaster. The sleep interval between retries while attempting to lock mailbox files with a lockfile-based locking protocol. On systems where sleep has a 1 second granularity, this value should be at least 2. Mailbox lock files are created with this mode. The number of times to attempt to lock mailbox files using a file-based locking protocol. This string will be expanded to form From: or Sender: fields. The expanded string must begin with "From:", which may be replaced by other strings to form an actual header field. The default value is:
	From: $sender${if def:sender_name: ($sender_name)}
The priority, or grade, characters corresponding to particular values of the Precedence: field in the message header. The parts of the string are separated by `:' with alternating precedence string and grade character. Numbers are higher in priority than upper case letters which are in turn higher than lower case letters. Also, lower numbers are higher in priority than higher numbers, and the same goes for letters lower in the alphabet. Grades in the range [a-m] will only have an error message and header returned to the sender on errors, rather than including the message body as well. Grades in the range [n-z] will not have anything returned to the sender on errors.

The precedence names recognized by many BSD sendmail configurations are: special-delivery, first-class and junk. Others are useful mainly for getting mail out of the local machine or for communication with other machines running smail in a similar configuration. The grade character for a message is available in string expansions as the $grade variable. The length of an internal address hit table. Addresses are hashed into this table to prevent multiple deliveries to the same address. Longer tables speed address hashing at a small memory expense.

NOTE: this value may be ignored in the future. Specify the timeout for locking a host's retry file for the purpose of exclusive delivery to that host. If the file cannot be locked within the specified time, then the message is not delivered; unless other considerations intervene, the message is left in the message queue (deferred). A number with no suffix indicates seconds. Suffixes can be added to indicate a time multiplier. m indicates minutes, h indicates hours, d indicates days. A colon-separated list of names for the local host. This list, together with uucp_host and more_hostnames should represent all possible names for the local host. Note that the visible_name hostname is not recognized as a name for the local host unless it also appears in the value for one of the other hostname variables. For a host that is in more than one domain or that can gateway to more than one level of domains, this should represent those names. For a host in a registered domain in the UUCP zone, which is also in the maps distributed over USENET, localhost.uucp should also be in the list. The first value in hostnames is used internally as a special ``primary name'' for the local host.

    If hostnames is set turned off (which is generally the default) then the hostnames value will be computed by pairing the localhosts's name, computed in a system-dependent manner, with all values in the domains attribute list. If this is on, then input spool file locking is always based on lock files. Otherwise, an inode-based locking mechanism may be used, such as flock(2) under BSD, or lockf(3) under System V. Inode-based locking is more efficient, if available. However, lock files can be easily created by shell scripts which may be advantageous under some circumstances. The creation mode for lock files. The creation mode for the various mail system log files. The name of a file to which transaction and error messages are appended. If this file does not exist, it is created with a mode from the log_mode attribute. If the hop count for a message equals or exceeds this number, then attempts at remote delivery will result in an error message being returned to the sender. This is used to prevent infinite loops. The hop count for a message can be set using the -h option when invoking smail. Otherwise it is computed from the number of Received: fields in the message header. For systems on which a load average can be computed, this specifies the maximum load average at which mail delivery will be performed, otherwise this value is ignored. If the load average exceeds this number, incoming mail will be saved in the input spool directory, though no delivery will be performed. If this value is 0 the load average will not be computed and delivery will always be performed. Normally the load average refers to a 5 minute load average. (This is not currently implemented) Messages longer than this will be truncated by smail when when written to its input queue. (This is not currently implemented and there is no limit on the size of messages). The size of an internal buffer for reading and writing messages. For systems with a reasonable VM space, this can be equal to the maximum size for messages. Specifying the value of in which case reading messages and then delivering them to one or more destinations requires very few read calls, as the entire message is always kept in memory. BUFSIZ, here, refers to the defined symbol in /usr/include/stdio.h. This string will be expanded to form the Message-Id: header field. This will be used if such a field does not already exist in the header. Each message has associated with it a unique file containing a transaction log for that message. This number specifies the creation mode for this log file. If a method attribute for a router does not specify a pathname beginning with `/', then this directory is prepended to the path to form the complete path for the method file. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. See the description of the router file for more information on method files. A colon-separated list of hostnames. This list is in addition to any names which may have been computed from the domains attribute in forming the value of hostnames. Thus, it is useful for specifying names which are not formed from the computed name for the host.

    The more_hostnames attribute can also be specified as gateway_names, since the attribute is often used to indicate the list of domains for which this machine is a gateway. This names a default user that defines permissions when no other user is specified. Also, this user is used in some conditions when it is not certain whether a set of actions can be trusted, if performed under other, potentially more powerful users. This should reference a login id which has few or no capabilities for doing harm or accessing protected files. The name of a file to which panic and very important error messages are appended. If this file does not exist, it is created with a mode from the log_mode attribute. Entries written to this log file represent problems that require human intervention, such as configuration errors or directory permission errors preventing mail spooling or delivery.

    Configuration errors generally cause mail to be moved into a special error/ directory under the input spool directory, thus preventing attempts at redelivery until the configuration error has been corrected.

    Thus, both the panic log and the error/ directory should be checked periodically under normal use, and frequently after configuration changes. When any problems have been resolved, these messages can be requeued for delivery by using mv(1) to move the spool files back to the spool directory. This is the default address for the postmaster. If the address Postmaster is not resolved by any of the configured directors, then this address is used. Names the file containing the hostname qualification information. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. If this is set then smail will not immediately attempt delivery for incoming mail. The smail program will then only attempt delivery when explicitly processing the input queue, such as when invoked with the -q flag. This string will be expanded to form the Received: header field. This field will be inserted into the header if the received attribute is not explicitly turned off for a transport. The default value for received_field is:
    	Received: \
    	    ${if def:sender_host\
    	         {from $sender_host by $primary_name\
    	          ${if def:sender_proto: with $sender_proto}\
    	          \n\t(Smail$version #$compile_num) }\
    	     else{by $primary_name ${if def:sender_proto:with $sender_proto }\
    		  (Smail$version #$compile_num)\n\t}}\
    	    id $message_id; $spool_date
    If this is not set, then configuration files are not required to exist. This applies to the primary and secondary config files and the director, router and transport files. If one of these files does not exist then it is ignored and internally compiled configuration is used instead. If this attribute is set, then any configuration file, which does not have a NULL filename (for example, using -router_file to set the name for the router file to NULL) and which does not exist, will generate a panic message from the mailer. Names the file containing the retry control information. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. Specify the default duration for attempting deliver of messages. If a message cannot be delivered within this period of time, then the message delivery fails and a bounce message is sent to the sender, or to the list owner, if there is one. A number with no suffix indicates seconds. Suffixes can be added to indicate a time multiplier. m indicates minutes, h indicates hours, d indicates days. Specify the default retry interval for connecting to unaccessible hosts. If a host is temporarily unreachable, then smail will avoid attempting to deliver to that host until this period of time has elapsed. This applies to all messages, so that queue runs will not block each message waiting for a timeout for a particular set of unaccessible hosts. See the description of the retry file for more information. This string will be expanded to form the Return-Path: header field. This field will be inserted into the header if the return_path attribute is turned on for a transport. Names the file containing the router configuration information. If this does not begin with `/', it will be referenced relative to the smail_lib_dir directory. This names a secondary configuration file which can define attribute values which override internal defaults and values in the primary configuration file. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. This is primarily useful in networks containing machines that share filesystems. By having a shared primary configuration file most systems on a network need not be concerned with maintaining the smail program, while other systems may want or need to use a different configuration, while sharing the same binary. In particular, the smart_user, smart_path and smart_transport attributes are common attributes to be set in the secondary configuration file. This names an environment variable that can be used to name the sender. Normally, the sender is determined from system login information, or by checking the real user ID of the calling process. If sender_env_variable is set, and an environment variable with the given name exists, then use it, by default. This can be set to LOGNAME for use with System V-based systems, or USER for BSD-based systems. Name a valid path to a smail binary that can be used to re-exec smail when a major configuration change has been detected, or to exec smail when delivering error messages. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. This defines the path to the smail configuration file directory. The router, director and transport files, as well as alias and path files and method files may be referenced relative to this directory. This defines the path to directory containing most smail utilities. In particular, smail expects to find the mkaliases and mkdbm utilities in this directory. This defines the default value for the path attribute used by the smarthost router driver. This gives the path to a machine which supposedly contains a more complete routing database than is available on the local host. See a later section describing the smarthost driver for more information on the use of this attribute. This defines the default value for the transport generic attribute used by the smarthost router driver. See a later section describing the smarthost driver for more information on the use of this attribute. This defines the default value for the smart_user attribute used by the smartuser director driver. The maximum number of SMTP connections that smail will process at any one time. This is for use with SMTP daemons started with the -bd option to smail. If connection requests come in while when this number of SMTP-connection children are forked, the connection will be shutdown with SMTP message 421.

    If this value is zero, then the number of SMTP connections is not limited. If this number of SMTP connection processes is exceeded, then additional connections will be accepted, but their messages will be queued and will not be processed until a later queue run. When the number of current connection processes drops below this number, immediate mail processing will resume, depending upon the value of delivery_mode.

    If this value is zero, then SMTP connections will not be converted to queue-only mode based on the number of connections. Note that the value of smtp_accept_queue should be less than the value of smtp_accept_max, and that setting smtp_accept_max to zero prevents smtp_accept_queue from working correctly in all cases. This string will be expanded to form the SMTP startup banner that is written by the SMTP server when a connection request is accepted. Each line of this message is automatically preceded by a 220 identification code, and newlines are correctly changed into a carriage-return newline sequence. The default value for smtp_banner is:
    	$primary_name Smail$version #$compile_num ready at $date
    This boolean variable controls the meaning of the DEBUG command when receiving SMTP commands. If the variable is on, then the DEBUG command (with an optional debugging level) sets debugging to the specified level, or 1 if no level was specified. The debugging output will be written over the SMTP connection. This interval defines the timeout for each SMTP receiver command for interactive SMTP daemons. If a command is not received within this period of time after a prompt, then the connection is closed down and the SMTP receiver exits. This interval defines the timeout for reading a message with the DATA command for interactive SMTP daemons. If the entire message is not received within this period of time after the ``354 Enter mail'' prompt, then the message is removed, the connection is closed down, and the SMTP receiver exits. This defines one or more directories into which incoming mail can be spooled. Directories are separated by single colon characters. When writing a message to the first spool directory fails, (say due to permission problems, filesystem full errors, etc.) successive spool directories are tried until the incoming message can be successfully written or until no more alternative directories exist. Each spool directory is expected to have writable subdirectories of: input (to hold the actual spool files), lock (for temporary lock files), msglog (for temporary per-message transaction logs and audit trails) and error (to hold messages which failed due to configuration errors or other problems which require human intervention). This character names the default grade for messages. This can be overridden by a Precedence: field in the message header. The grade is used in sorting messages in the input spool directory and is also available in string expansions as the $grade variable. See the grades attribute for more information. This defines the file creation mode for spool files. names the file containing the transport configuration information. If this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. This names a list of users (separated by colons) who are trusted to specify a sender for a message. Users who are not in this list cannot specify a Sender: header field without it being removed. If such users specify a From: header field, then a Sender: field will be created that specifies the real user that submitted this mail. Generally, this should be set to that names of all users under which remote mail is received and sent to smail. If this list is turned off, using the form -trusted, then all users are trusted.

    NOTE: The real user ID is used in verifying trusted users. However, under many operating systems, the /usr/lib/uucp/uucico program runs under the real uid of the user that ran /usr/lib/uucp/uucico. Often any user can run the uucico program. The smail program cannot differentiate this case from any other case and will thus do the ``wrong thing'' here. If this problem exists on your machine, then the trusted attribute may need to be turned off. This problem is particularly difficult to resolve on System V machines where non-superuser programs are unable to change their real uid. This names a list of groups (separated by colons) that are trusted to specify a sender for a message. The groups specified are checked against the effective gid of smail. Thus, if smail is a setgid program, then this string is of no value and should be turned off. However, if smail is not set gid, then programs that invoke smail under a specific effective gid, while not a specific real uid, can be detected and can be properly treated as trusted. This specifies a name for the local host. This name is available in string expansions as the $uucp_name variable. It is also used in the ``remote from hostname'' suffix to ``From<space>'' lines for mail being delivered to remote machines, when the from attribute is turned on for a transport. The full domain name used in outgoing mail addresses within header fields. If visible_name is turned off, then it will be set to the first name from the hostnames attribute. If the hostnames attribute is not specified then that attribute will be filled in with hostnames of the form hostname.domain, where hostname is derived in a system-dependent manner and where domain, here, is one name from the domains list attribute. Each entry in the domains list is used, in order, to created the hostnames value.

    For sites in the UUCP zone domains will often merely be the string ``uucp''. Finally, the variable $visible_name is available in string expansions.

    For compatibility with earlier versions of smail3.1, the domains list can also be specified as visible_domains.

DIRECTOR, ROUTER AND TRANSPORT FILE FORMATS
The director, router and transport configuration files share a common format, which is described in this section. The specific contents for each file are described in later sections.

Each entry in one of these files specifies a name for the entry, a set of generic attributes and a set of driver attributes. The generic attributes and the driver attributes define the characteristics for the entry.

The list of possible generic attributes are common to all entries in a configuration file. One generic attribute is always required: the driver attribute. This attribute names the underlying set of functions that will be used when using that entry. The list of possible driver attributes are specific to different types of drivers.

The form of an entry is:
	entry_name:
		generic_attribute , ... ; driver_attribute , ...
where a comma separates the definitions for specific attributes and where a semicolon separates the generic attributes from the driver attributes. It is not an error for an entry to end in a comma or semicolon. The form for generic and driver attributes is the same as for entries in the config file.

As an example, consider an entry in the transport file that specifies use of the program /bin/mail to deliver mail to local users. The mail messages are to contain a ``Return-Path:'' header field, and the /bin/mail program is to be given no more than 20 addresses per invocation. A simple entry to specify this is:
	# call /bin/mail to deliver to local users
	local: max_addrs=20, return_path, driver=pipe;
		cmd="/bin/mail $($user$)"

INTERACTION BETWEEN DIRECTORS, ROUTERS AND TRANSPORTS
To better understand the use of the director, router and transport files, this section describes, briefly, how address resolving and delivery is accomplished in smail. The configuration specified in these files is intimately involved in this process.

When smail is given a list of addresses to which a message is to be delivered, the list is processed iteratively until a list of resolved addresses is produced. When an address is resolved, the transport (the part of smail that performs delivery of messages to local users or remote hosts) and all data required by the transport will be known.

To accomplish this the smail program goes through the following steps:

a.  Each address is parsed to find a hostname, called the target, and the remaining part of the address, called the remainder. As a simple example, in the address tron@uts.amdahl.com, the host part uts.amdahl.com is the target and tron is the remainder. In the address sun!amdahl!tron, the target is sun and the remainder is amdahl!tron. More information on addresses can be found in mailaddrs(5).

b.  Each local address is given to directors, in the order specified by the director file, until one of the directors says that it knows what to do with that address. That director has the option of returning a new list of addresses or of putting the address on a list of resolved addresses. If new addresses are produced, they are put on the input list, to be processed from step a.

c.  Each remote address is passed to routers, in the order specified by the router file, until one of the routers is able to match the target name for the address. If no router is able to match the complete target, then the first router with the longest match will be used. The router specifies the transport to be used for delivery to that address, plus some other information required by the transport, such as the next host and next address values. The transport may come from a router default, a method file of may be specified by the router specifically.

When all addresses have been resolved, they are sorted out and passed to transports. It is the job of the transport to deliver a message to the set of addresses that it is given.

It is important to know that all hostnames and local usernames are matched independent of case, so that, for example, Postmaster, POSTMASTER and postmaster all compare equal. In addition an internal hash table is kept of all regular recipient addresses, that is, all addresses which do not specify files or shell commands. This table is used to discard duplicate regular recipient addresses. This hash table is independent of case, as well, so that the address Postmaster@SRI-NIC.ARPA is considered a duplicate of postmaster@sri-nic.arpa.

THE DIRECTOR FILE
The director file describes the operations, and their order, for handling local addresses. For example, some possibilities are to expand a local address into a list of local and remote addresses through an alias file, forward file or mailing list, or to cause mail to be delivered to a local user.

The following list describes the possible generic attributes for director file entries: If set then be cautious of addresses produced by this director. If the nobody attribute is not set, then reject file, shell command or :include:filename-style mailing list addresses. If the driver does not associate a group to an address returned by it, then associate the group id for this group name. This will override the gid set by a default_user attribute. If the driver does not associate a home directory with an address returned by it, then use this home directory. The value will be expanded to form the actual directory pathname. At the present time, the $user variable is not available for this expansion. If the string expansion fails, it is ignored. If the driver does not associate a user or group to an address returned by it, then associate the user id and group id of this user. The driver attribute names a specific set of low-level functions which will do the work of directing local mail. This attribute is required. If set, then access files, or run shell commands as the user specified by the nobody attribute, for addresses flagged with caution by either the caution generic attribute or by the driver. Association of nobody with an address overrides the default_user, default_group, set_user and set_group attributes. This attribute is set by default. Names the address to be sent mail if an error occurs in processing the addresses produced by this director. This string is expanded with the variable $user set to the local-form address passed to the director. Commonly the value will be ``owner-$user''. If this string expansion fails, it is ignored. If set, then it is always okay for this attribute to produce an address equal to the sender. This effectively turns on the me too flag for this director. This should generally be set for forwarding directors and should not be set for aliasing and mailing list directors. Associate the gid for this group with the addresses returned by the driver. This overrides any gid set by the set_user attribute. Associate this home directory with all addresses returned by the driver. This will be expanded in the same manner as default_home. Associate the uid and gid for this user with addresses returned by the driver. This overrides any values set by the driver.

There are two addresses which are required by the mailer software to exist: the address Postmaster and the address Mailer-Daemon. To avoid the necessity of an alias for these two users, smail contains two implicit directors embedded into the directing code. These implicit directors are used as a last resort. The first such director maps the address Mailer-Daemon onto the address Postmaster and the second maps Postmaster onto the address root.

THE ROUTER FILE
The router file describes the operations, and their order, for handling remote addresses. For example, some possibilities are to lookup hostnames in a routing database, to match a special domain-literal form, or call a program to return a list of neighboring hosts.

The following list describes the possible generic attributes for router file entries: Routers will not always find a complete match for a particular hostname. For example, if a routing database has a route to the domain amdahl.com but not to the hostname futatsu.uts.amdahl.com then the routing driver might return the route to amdahl.com. Generally, the route for the longest match of the target host is used. However, if the always attribute is set, then any match found by this router will be used in preference to routes that might have been returned by routers later in the router list. This is useful for hardwiring a certain number of routes within a small database. For example, this is useful for Internet sites that gateway for a small number of UUCP sites in the UUCP zone. The driver attribute names a specific set of low-level functions which will do the work of routing remote mail. This attribute is required. The router driver has the option of specifically setting a transport to use for remote delivery. If the driver does not do so, then either a method or a transport attribute must exist to specify how the mail is to be delivered. A method attribute specifies a file which contains a table relating hostnames to transports. A transport attribute specifies a specific transport. If the method file does not contain a match for all hosts, then the transport named with the transport attribute is used. The format of a method file is given in the next section.

METHOD FILES
Method files define a relation between a set of hostnames and a set of transports to be used in delivering to those hostnames. Method files use the standard routine for reading file entries, just as with the config, director, router and transport files. Each entry should have the form:
	hostname	transport-name
stating that mail being sent to hostname should be delivered using the transport transport-name. As a special case, if the hostname value is the special string ``*'', the entry matches any host. This is a catch-all feature which should only be used in the last entry in a method file.

Entries in a method file can be associated with particular message grades. This allows different grades to use different transports, such as non-demand UUCP for messages with a bulk or junk precedence. Grade ranges are specified by appending a grade letter range to the hostname, separated by /. Entries with grades can be in any of the forms:
	hostname/X	transport-name
	hostname/X-*	transport-name
	hostname/*-Y	transport-name
	hostname/X-Y	transport-name
See the definition of the grades configuration variable for a discussion of grade letters, and their correlation with message precedence strings. In the first form, the transport is used for an exact match of the grade letter. In the second form, a match requires a grade a character value of at least X. In the third, form a match requires a grade character value of at most Y. The final form specifies a range of grades from character value X to character value Y.

For example, with the default value for the grades variable, the following file will use smtp for hosts local1 and local2, if the precedence is air-mail or better; otherwise, for any host with a precedence of first-class or better, demand-polled uucp is used; otherwise, queued uucp is used:
	local1/*-A	smtp
	local2/*-A	smtp
	*/*-C		demand_uucp
	*		uucp

THE TRANSPORT FILE
The transport file describes the various possible ways, of delivering mail. For example, some possibilities are to call a program such as uux(1) to deliver mail to a remote host, to connect over TCP/IP to a remote host and converse using an SMTP protocol, or to deliver local mail by appending to a user's mailbox file.

NOTE:
    Unlike the routers and directors files, the transports file does not replace all compiled-in transports. Rather, entries in the transports file override existing entries of the same name, or add new entries. Thus, if you wish to add one new transport definition, you need only add the new definition, and do not need to duplicate all of the existing entries.

The following list describes the possible generic attributes for transport file entries: Use a batched SMTP format, where the message is enclosed in an envelope of SMTP commands. This is not the same format commonly used on BITNET, as it does not contain FORTRAN carriage control characters. This can be used to send mail to remote hosts using SMTP formats even when direct two-way connections are not feasible. For example, this will work over UUCP and eliminates difficulties with sending arbitrary addresses as arguments to UUX. Use of bsmtp also turns on the dots attribute. When used with the uucp attribute, UUCP-style !-path addresses are used in the SMTP envelope. If set, then each line of the header and message will end in carriage-return/line-feed rather than a single newline character. This is not typically useful, as the SMTP transport, which requires this as a part of the interactive protocol always does this anyway. If set, replaces the body of the message with debugging information. This can be used, for example, as a shadow transport to watch the flow of mail for a while for debugging purposes. This essentially allows for debugging without the ethical and space problems of saving the personal correspondence of others. If set, then use the hidden dot protocol. All output lines which begin with dot will have one more dot prepended. All of the various SMTP modes imply this behavior. The driver attribute names a specific set of low-level functions which will do the work of delivering mail. This attribute is always required. names another transport that the message should be sent to, if the first transport returns failure. If set, then supply a ``From<space>'' line before the message when delivering with this transport. If this is a remote transport (i.e., the local attribute is not turned on) then this line will end with ``remote from hostname'' where hostname is the UUCP name for the local host. This is useful for delivery over UUCP and for delivery to standard mailbox files, which require this format. ``Half-baked'' batched SMTP. This is batched SMTP mode without an initial HELO command or an ending QUIT command. This can be used for creating files which will be concatenated together at a later time to form one batch of SMTP commands containing multiple messages. Use of the hbsmtp attribute also turns on the dots attribute. If set, the form of the header and envelope information will be setup for delivery to the local host. This performs no changes to existing header fields, other than insertion of commas into fields containing sender and recipient addresses. This also affects the form of any generated ``From<space>'' line and the form of envelope addresses used in SMTP commands.

    This can be used with remote delivery, if delivery is to a remote smail3.1 site, which is useful within a domain that maintains consistent user forwarding information. This leaves messages in unqualified format until leaving the domain through a gateway. This implies local_xform, but implies that delivery really is final delivery to a user, file, or program on the local host. This disables generation of a bounce message resulting from an excessive message hop-count. This states the maximum number of recipient addresses that can be given in one call to the transport. If this is turned off then there is no maximum number. The default number is 1 and typically this is either left as 1 or turned off. This states the maximum number of characters in recipient addresses that can be given in one call to the transport. If this is turned off then there is no maximum number. The default number is about one third of the number characters that can be passed as arguments to a program. When using SMTP transports this should be turned off unless a remote host is known to be unable to handle a large number of addresses. For delivery over UUCP to a remote rmail program, this should be around 200 or 250, to avoid buffer overruns at the remote site. UUCP generally has small buffers to hold argument information.

    If smail is given an address whose length exceeds this number, then the address will be passed with one call to the transport. Thus, this limit is not strictly enforced. This states the maximum number of different hosts that can be given in one call to the transport. If this is turned off, using the form -max_hosts then there is no maximum number. The default number is 1 and typically this is not changed. If set, then a Received: field is inserted for mail being delivered with this transport. The form of this field is taken from the received_field attribute in the config file. This attribute is on be default. If set, then a Return-Path: field is inserted for mail being delivered with this transport. The form of this field is taken from the return_path_field attribute in the config file. This should only be used for transports which perform final delivery to local destinations. This names another transport that the message should be sent to. This could be used to, for example, start a program that looked up the sender in a database and brought up a rendition of his face from a face server in a window on your workstation. The shadow transport is called only if the primary transport successfully performs delivery. If this flag is set, then some effort is done to transform mail which does not conform to RFC822 standards. This is potentially useful for sites which gateway between the UUCP zone and the Internet. In general, it is not a good idea to turn this on as it changes the contents of headers fields. This should only be done when it is known that some remote hosts only understand mail which conforms to the RFC822 standard. If set then any line in the body of the message which begins with ``From '' will have the character `>' inserted at the beginning. This is required for local delivery to mailbox files that are in the standard form expected by the System V mailx (1) and the BSD Mail (1) programs. If set then outgoing recipient addresses will be converted into UUCP-style paths of the form hosta!hostb!hostc!user. An exception is that any use of `%' as an address operator is preserved. Thus, an envelope address of user%hostb@hosta would be converted to hosta!user%hostb. This only affects envelope addresses and does NOT affect the message or the message header. If set then outgoing recipient addresses will be conform into to internet specifications. This is not the same as the strict attribute, since the transformations apply only to the envelope addresses, and not to headers. If inet is defined, then route-addr addresses will be generated when routing to remote destinations, rather than !-style addresses. Thus, if smail is given the address user%host@gateway and gateway is reached through the path hosta!hostb!hostc, then smail will generate the address @hostb,@hostc:user%host@gateway to be sent to the host @hosta. The subdirectory under X_MAIL_SPOOL_DIR_X/retry to use for managing host retry intervals for this transport. By default, the name of the transport is used. However, multiple transports can share a retry directory by setting retry_dir for several transports to the same value. For example, by default all of the default TCP/IP SMTP transports (inet_zone_smtp, uucp_zone_smtp, and local_smtp set retry_dir to ``smtp''. Identify a header field that will be removed from the message for transport. This is an expansion string, so header removal can be made dependent upon some conditions. If expansion of the string results in an empty string, then no header is removed. Any number of remove_header attributes can be specified. Add the given header field at the beginning (insert_header) or end (append_header) of the message header for transport. These are expansion strings, so the header (and the existence of the header) can be made dependent on some conditions. If expansion of the string results in an empty string, then no header is added. Any number of insert_header and append_header attributes can be specified.

As an example of the manipulation of headers, consider the addition of an ``Organization'' header for all locally generated mail that does not already have an Organization header. This can be done with:
	append_header="${if and{{origin:local}{!header:organization}} \
		Organization: ACME Explosives Corp.}"
To configure a ``Content-Length'' field, which some systems use to identify the length of a message within a mailbox file rather than keying on lines starting with ``From'', use:
	remove_header="Content-Length",
	append_header="Content-Length: $body_size"

THE QUALIFY FILE
This section details the format and use of the hostname qualification file.

The qualify file defines the domain name(s) to be used in making all hostnames fully-qualified. Note that this file is used only for bare hostnames, i.e. names without dots.

The qualify file uses the standard routine for reading file entries. Each entry should have the form:
	hostname  domain
stating that the host name hostname should be considered a part of domain domain. As a special case, if the hostname value is the special string ``*'', the entry matches any host. This is a catch-all feature which should only be used in the last entry in a qualify file. Typically, UUCP sites should should have an entry like:
	*         uucp
at the end of the qualify file.

If the qualify file is missing, or if no entry is found that matches a given hostname, then no hostname qualification is performed.

THE RETRY FILE
This section details the format and use of the retry control file.

The retry file defines, by target domain, the minimum interval between delivery attempts and/or the maximum duration over which to continue attempting delivery.

Each retry entry should have the form:
	domain[:domain...]  [interval]/[duration]
stating that, for the given domain(s), delivery will be attempted no more frequently than interval, and that delivery attempts will cease after duration.

Values for interval and duration are in seconds. However, they can be written as a sequence of numbers with suffixes of `s' for seconds, `m' for minutes, `h' for hours, `d' for days, `w' for weeks and `y' for years. For example, 10m/2d specifies an interval of ten minutes and a duration of two days.

Either or both of interval and duration may be omitted, in which case they are taken to be zero (i.e. no limit).

As a special case, if a retry file entry has a domain list equal to the special string ``*'', that entry matches any domain. This feature is a catch-all which should only be used in the last entry in a retry file.

If a retry file contains no ``*'' catch-all entry, then the configuration parameters retry_interval and retry_duration will be used to control retries to domains without specific retry entries.

THE DIRECTOR DRIVERS
This section details the usage and driver-specific attributes for all of the director drivers distributed with smail. See the section THE DIRECTOR FILE for more information on directors.

The Aliasfile Driver
The base standard for the format of the aliases and forward files should be the format used by the BSD sendmail program. This format is simple yet powerful enough for most needs.

A sendmail-compatible aliases file consists of relations between alias names and the lists of entities to that the aliases expand. Each entry is of the form:
	alias-name: address, ...
The following is a sample alias file for a machine nsavax:
	# Sample aliasing file for nsavax
	root: brown, casey	# redirect root's mail
	MAILER-DAEMON: postmaster
	postmaster: brown	# brown maintains netnews and mail
	netnews: brown
	north: north, fawn	# copy fawn on all north's mail
	# post important information to network
	msgs: local-msgs@ciacray, local-msgs@nscprofs,
		local-msgs@nsavax
	local-msgs: "|/usr/ucb/msgs -s"	# deliver to msgs program
	# administrivia
	rnews: |/usr/lib/news/uurec	# read news messages from mail
	# mailing lists for accessing users on the local network
	nsavax-users: :include:/usr/lib/mail/nsavax-users
	ciacray-users: :include:/usr/lib/mail/ciacray-users
	nscprofs-users: :include:/usr/lib/mail/nscprofs-users
	# mail to everybody on the local network
	everybody: nsavax-users,	# well, almost everybody
		ciacray-users,
		nscprofs-users
	# save mail to mailing list requests and send to moderator
	funding-request: /usr/log/funding-req, reagan@nscprofs
	covert-bugs-request: /usr/log/covert-bugs-req, james.bond@ciacray
	# broadcast to mailing lists, and save a copy
	funding:	# excludes congress
		:include:/usr/list/funding,
		/usr/log/funding	# save all messages here
	covert-bugs:	# includes kgb
		:include:/usr/list/covert-bugs,
		/usr/log/covert-bugs	# save all messages here
The aliasfile driver searches for matches between a local address on input and an alias-name from the alias file. If a match is found, it returns the associated list.

It has the following driver attributes: Define the name of the file containing the database. Except when this is not appropriate for the proto being used, if this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. A sleep interval between open retries, in seconds. On systems which have 1 second granularities on wakeup times and where, as a result, sleep times can be nearly 0 seconds, this number should be at least 2. A mask, ala umask(2), defining the maximum permissiveness allowed for the permissions on the alias file. For example, a modemask of 022 disallows write access to all but the file owner. This value should be chosen to strike a reasonable compromise between security and user convenience. It should also take into account the use of the owners and owngroups attributes described below. A paragraph below describes the consequences for a file not meeting this criteria. If set, then if the open fails, assume an empty alias file. This is useful for optional databases. For example, in a networking environment, workstations may be configured with the option of having a private alias file, without the necessity of creating such a file on each host. A list of permissible owners for the alias file. A paragraph below describes the consequences for a file not meeting this criteria. A list of permissible owning groups for the alias file. A paragraph below describes the consequences for a file not meeting this criteria. Names the protocol used in opening and searching the database. Possibilities are discussed below. If this attribute is on, the alias file will be closed and reopened after each call to the driver. This is useful for systems that have a shortage of file descriptors yet wish to access a large number of databases. the maximum count of open retries. This should be greater than zero if the system does not have an atomic rename(2) system call, as the alias file may not always exist while being modified. If set, then if the open fails, the resolution of local addresses will be attempted at a later time. This is useful in a networking environment where failure to open a database (such as a remote YP database) may be a result of a server machine being down or temporarily inaccessible.

If any of the attributes modemask, owners or owngroups reject the file as a possible security problem, all addresses returned are flagged with the caution bit set. See the generic director attribute nobody for more information.

The current list of possible values for the proto attribute is:

bsearch
    Use a binary search to look through a sorted file arranged as lines which begin with a key and are followed by the value associated with the key, separated by a colon or whitespace. The file should be sorted by the key, not by the line. The mksort(8) utility sorts lines correctly. Care should be taken when using the regular sort(1) to ensure that the sort uses proper delimiters.

dbm Use the BSD dbm(3x) or ndbm(3x) routines to search for the key. The keys and data in the dbm database must end in a nul byte. If only the dbm(3x) library is available then only one dbm database can be used by smail , while the ndbm(3x) routines will allow any number of databases. However, it is always okay for multiple routers and directors to use the same dbm database, if this is useful.

aliasyp
    This is a variant of the yp protocol that is compatible with the standard Sun mail.aliases YP service. This database has a different format from other databases which must be taken into account when sending requests. Typically this is not useful for a path database.

lsearch
    Use a linear search using the same read routine used to read config files. `#'-style comments are allowed and the beginning of each file entry should be the key, followed by whitespace or a colon character. The rest of the entry should be the value associated with the key.

yp  Use the Sun YP service to access a paths database stored on a remote machine. In this case the value for the file attribute is of the form:
    domain_name:database_name
where the domain_name: is optional and defaults to the default YP domain for the local host.

nialias
    Use the NeXT NetInfo database, for getting user aliasing information.

A simple entry in the director file is:
	# don't perform any authentication on the alias file
	aliases: driver=aliasfile;
		file=/usr/lib/aliases, proto=dbm

The Forwardfile Driver
Sendmail-compatible forward files have the same structure as mailing lists. This format is:
	address, address, ...
Where newlines can be included wherever whitespace is allowed, and where a `#' character begins a comment that ends at the end of the line. Comments are treated as whitespace.

An example forward file for the user james.bond on nsavax is:
	# send to my own machine, but keep a copy here
	# just in case it doesn't make it there.
	bond%british-ss@ciacray, james.bond

A useful forward file is:
	# I am on vacation, save away my mail, but tell people
	# I won't be back for a while
	hustead,
	"|mailx -s 'Yep, gone fishing!' \"$SENDER\" < $HOME/.fish"
Which will save to Ted Hustead's mailbox file and will also execute the following shell command:
	mailx -s 'Yep, gone fishing!' "$SENDER" < $HOME/.fish
where the shell variables $HOME and $SENDER are available from the environment as the user's home directory and the sender address, respectively. Note that if the ignore_write_errors attribute is not turned on in the pipe transport, this example will cause mail to be returned to the sender stating that a write error occurred on the pipe to mailx. To prevent this, the line could also be changed to:
	"|cat>/dev/null;\
	 mailx -s 'Yep, gone fishing' \"$SENDER\"<$HOME/.fish"
where the ``cat>/dev/null'' will read stdin, preventing a write error on the pipe.

The current list of driver attributes for the forwardfile driver is: This string defines a list of users and directories which should cause addresses to be flagged with caution. Each entry in the list is expanded individually. If this string expansion fails, it is ignored. A number, or a number range (in the form low_number-high_number) can be used to indicate numerical uid's that should be treated with caution. Typically, this string is ``0'', thus preventing file and shell command from being performed as the superuser, ``0-99'', preventing access with a system id. If set, then one of the permissible owners will be the user associated with the forward file. The name of a file containing the forward information for a user. This string will be expanded with the local name passed to the director available as $user and any associated home directory available as $HOME. If this string expansion fails, it is ignored. If set, then the file must begin with ``Forward to '' to be considered a forward file. Also, only the first line is scanned for addresses. This ``feature'' mimics the capability found in some systems for hiding forwarding information in user mailboxes. A mode mask defining the maximum permissiveness allowed for the permissions on a forward file. Analogous to the modemask attribute for the aliasfile driver. This attribute requires that an address begin with the specified string to be matched by the director. In addition, any reference to the $user variable in the file attribute will have this prefix removed. This attribute requires that an address end with the specified string to be matched by the director. In addition, any reference to the $user variable in the file attribute will have this suffix removed. Both a prefix and a suffix attribute can be specified for a director. In this case both the prefix and the suffix string are required for a match. Specifies a list of user who may own the forward file. Specifies a list of groups who may own the forward file. This string defines a list of users and directories which should cause addresses to be flagged with unsecure. This will prevent delivery to shell commands or files. Each list entry is expanded. If this string expansion fails, it is ignored. A number, or a number range (in the form low_number-high_number) can be used to indicate numerical uid's that should be treated with caution.

If none of the attributes owners, owngroups or checkowner is given, no checks are made on ownership restrictions. The default modemask is 0, effectively disabling checks for file mode restrictions.

NOTE:
    Unless the file attribute references $HOME or begins with ``~/'' the forward file driver can be used to provide forward files for users or names that are not listed in the passwd file. In this case, $user merely expands to the address passed to the forwardfile driver. This feature can be used for setting up forwarding for obsolete accounts or mailing list directories.

The prefix and suffix attributes can be used to define mailing list directories associated with ownership or request addresses. To get a directory of mailing list or alias owners, a prefix of ``owner-'' could be used. To create a directory of request addresses, a suffix of ``-request'' could be used.

An example of useful forwardfile director entries are:
	# put forwarding addresses for obsolete accounts under
	# the /u/obsolete directory.  These will contain only
	# forwarding addresses.  This is maintained by users in
	# the group "admin" or "staff".
	obsolete:
		driver=forwardfile;
		file=/u/obsolete/$user,
		owngroups=admin:staff
	# handle per-user forward files in each user's home
	# directory.  This is roughly compatible with BSD
	# sendmail, though performs some access checks, and
	# is very cautious of directories which are remotely
	# accessible.  Root's .forward entries will operate
	# from the nobody uid.
	dotforward:
		driver=forwardfile, nobody;
		file=~/.forward, unsecure=~uucp:~ftp,
		caution=root, checkowner, owners=root,
		modemask=022
	# allow the "Forward to " feature to be used from user
	# mailbox files as used in System V.
	forwardto:
		driver=forwardfile, nobody;
		file=/usr/spool/mail/$user, caution=root,
		checkowner, modemask=002
	# define a mailing list directory, with any shell commands
	# executed under the nobody user id.  Any file in this
	# directory defines the name and contents of a mailing list.
	mailing_lists:
		driver=forwardfile, caution;
		file=/usr/lib/smail/lists/${lc:user}
	# define a directory of owner mailing lists.  Addresses
	# specified in this directory specify the owner address of a
	# mailing list or alias.
	owner_lists:
		driver=forwardfile, caution;
		file=/usr/lib/smail/lists/owners/${lc:user},
		prefix="owner-"

The Mailing-list Drivers
Mailing-list drivers come in two forms, one form for mailing-lists derived by aliasing drivers, and another form for mailing-lists derived by forwarding drivers. The reason for having two forms is that security options take different forms depending on where mailing-lists come from. Also, by having them separately recognized it is possible to allow pipes and files in mailing-lists from alias files but not from forward files. Note that if a new driver is written that does not comply to the standards for alias drivers and forwarding drivers, and that can produce mailing lists, a new mailing-list driver may need to be written as well.

The format of a mailing list file is the same as that of a forward file, a simple list of addresses, with optional comments.

The driver attributes are common to both of the mailing-list drivers: If set, attributes related to ownership restrictions are taken from the director which produced the mailing list address. The modemask is copied from the director which produced the mailing list address. The sleep interval, in seconds, between retries. For systems that have a 1 second timing granularity, this number must be at least 2 to guarrantee a non-zero sleep interval. Names the specific director that this entry matches expansions of. This can be used to assign different attributes from alternate uses of the aliasfile and forwardfile directors. The maximum permissiveness of file modes. A list of allowed owners. A list of allowed owning groups. The maximum count of open retries.

The User Driver
The user director directs mail to a mailbox for known user on the local host. It will succeed if the local address matches a user on the system and will put an entry on the list of fully-resolved addresses.

The driver attributes are: The prefix, if non-NULL, must be found in the front of the username for this driver to be used. This prefix is removed from the username prior to determining if it is a valid user on the local host. This can be used to set up an alternate name for each user on the system which is not matched by aliasing or forwarding director. Commonly, prefix will be set to ``real-'' for one of the directors, so that mail can be guaranteed to be delivered to a user's mailbox file on a specific host by mailing to an address such as ``real-tron@namei.uucp.'' If a match is found, the actual username is given to the transport. The name of the transport to associate with the address.

A typical user director entry in the director file is:
	user:  driver=user; transport=local
This will associate any mail destined for a user on the local host with the local transport.

The Smartuser Driver
It may be that you wish all local addresses that you don't recognize to be sent elsewhere. For example, there could be a host in your domain that knows where most of the domain's users reside. The smartuser driver is a convenient way of handling this case, by redirecting mail for unknown users to another host. Note that this must be the last director entry, if it is used, because it is generally non-discriminatory.

The possible driver attributes for the smart user driver are: This defines the new address to direct mail to. This string will be string expanded with $user set to the local address name, and with $HOME being any the associated home directory, if there is one. It is a configuration error for this string expansion to fail. If set, the smartuser driver only matches an address if it contains characters exclusively from the set of letters, digits, whitespace, as well as `-', `_', `+', and `.'.

If the well_formed_only attribute is on, any use of $user in the new_user value will have any groups of one or more whitespace and dot are characters collapsed into exactly one dot. If it is off, the $user value may be enclosed in double-quotes, with backslash escapes where appropriate. This prevents the the value of $user from changing the form of the address.

A sample entry is:
	smartuser:
		driver=smartuser;
		new_user=$user@gateway.domain,
		well_formed_only
With this entry, the input addresses:
	john
  and	John Q. Public
will become:
    john@gateway.domain
  and    John.Q.Public@gateway.domain
respectively. If well_formed_only had not been set, the second address would have been:
    "John Q. Public"@gateway.domain whereas the input address:
    \unusual"address"in\deed would become:
    "\\unusual\"address\"in\\deed"@gateway.domain Addresses which are produced by the smartuser driver are flagged as such and will not themselves be matched by the smartuser driver. Thus, infinite loops will not occur if ``gateway.domain,'' from the example, happens to be the local host.

It is possible to set the new_user value in the config file. This is done by setting the config file attribute smart_user. For example, the config file could contain the following line:
	smart_user = $user@gateway.domain
Then, if the entry in the director file was:
	smart_user: driver=smart_user; well_formed_only
the configuration would be equivalent to the second smart_user example above. This makes it possible to share copies of the director file among several machines, with the smart user configuration specific to one machine being set in its private configuration file. This config file attribute is used only if the new_user attribute is not given in the smart_user entry.

THE ROUTER DRIVERS
This section details the usage and driver-specific attributes for all of the router drivers distributed with smail. See the section THE ROUTER FILE for more information on routers.

The Pathalias Driver
The pathalias router computes routes from a database in the style produced by the pathalias program. It has the following driver-specific attributes: A list of domains to be stripped from the end of a hostname before it is searched for in the database. Multiple domains, in this list, are separated by colons. This defines the name of the file containing the database. Except when it does not make sense as a result of the proto used, if this does not begin with ``/'', it will be referenced relative to the smail_lib_dir directory. The number of seconds to wait between open retries. If set, then if the open fails, assume an empty alias file. This is useful for optional databases. For example, in a networking environment, workstations may be configured with the option of having a private alias file, without the necessity of creating such a file on each host. Names the protocol used in opening and searching the database. Possibilities are discussed below. If set, the pathalias will be closed and reopened after each call to the pathalias driver. This is useful in environments where file descriptors are scarce but many databases are desired. A list of domains which targets are required to be for a match. The names are not stripped, unless they are also specified by the domain attribute. The maximum number of retries for opening a file. This is useful on systems without an atomic rename system call. On such systems there will be a window of vulnerability when new databases are moved into place where no file will exist. A list of domains to be stripped only if the target was not found in the database without the domain stripped. (This is currently not supported). If set, then if the open fails, the resolution of local addresses will be attempted at a later time. This is useful in a networking environment where failure to open a database (such as a remote YP database) may be a result of a server machine being down or temporarily inaccessible.

The current list of possible values for the proto attribute is:

bsearch
    Use a binary search to look through a sorted file arranged as lines which begin with a key and are followed by the value associated with the key, separated by a colon or whitespace.

dbm Use the BSD dbm(3x) or ndbm(3x) routines to search for the key. The keys and data in the dbm database must end in a nul byte. If only the dbm(3x) library is available then only one dbm database can be used by smail , while the ndbm(3x) routines will allow any number of databases. However, it is always okay for multiple routers and directors to use the same dbm database, if this is useful.

lsearch
    Use a linear search using the same read routine used to read config files. `#'-style comments are allowed and the beginning of each file entry should be the key, followed by whitespace or a colon character. The rest of the entry should be the value associated with the key.

yp  Use the Sun YP service to access a paths database stored on a remote machine. In this case the value for the file attribute is of the form:
    domain_name:database_name
where the domain_name: is optional and defaults to the default YP domain for the local host.

aliasyp
    This is a variant of the yp protocol that is compatible with the standard Sun mail.aliases YP service. This database has a different format from other databases which must be taken into account when sending requests. Typically this is not useful for a path database.

All database lookups are either independent of case or, when case independent lookups are impossible, case-folded. Thus, keys in DBM or YP databases must be in lower case.

As an example of the use of the domain, try and required driver attributes, if the domain value is ``uucp,'' then any hostname that ends in .uucp will have the .uucp removed before being looked up. Alternately, if the the try value is ``uucp,'' then ``.uucp'' is stripped only if the original was not found. If the required value is ``uucp'' then a hostname is not a candidate for a match unless it ends in ``.uucp.'' The effects of domain and try are not cumulative and a hostname is applied to the required attribute value before being applied to domain and try in that order.

Note that the length of any stripped string is added to the count of characters matched for purposes of deciding which router had the most complete match.

A sample pathalias router entry is:
	pathalias:
		transport=uux, driver=pathalias;
		file=paths, proto=bsearch,
		domain=uucp
An example of a pathalias file for the site walldrug is:
	.amdahl.com	amdahl!%s
	amdahl	amdahl!%s
	dgcad	namei!glotz!nsavax!dgcad!%s
	glotz	namei!glotz!%s
	hoptoad	hoptoad!%s
	kgbvax	kgbvax!%s
	kremvax	kremvax!%s
	namei	namei!%s
	nsavax	namei!glotz!nsavax!%s

This data base associates a host or domain name, on the left hand side, with a path, on the right hand side. The right hand side should be a UUCP-style `!'-path ending in a ``%s''. The format is intended to be more general, with the ``%s'' showing where to put a user name. Indeed, pathalias(8) can produce paths involving both right and left operators such as:
	decwrl	decwrl!%s@ucbvax
This form is not recommended in general because of a historical disagreement over the precedence of ``!'' and ``@'' which is not always resolved correctly by the pathalias program. By standardizing on UUCP-style `!'-paths, as will be produced from the USENET maps, we avoid many routing ambiguities. If the path is just ``%s,'' it denotes a name for the local host.

The Uuname Driver
Some sites in the UUCP zone may wish to use a direct path to their neighbors, without relying on a pathalias database. Alternately, a site may wish to use the pathalias routes to their neighbors only in the case that a domain address is given (i.e., ``neighbor.uucp'').

A simple driver that meets these requirements is the uuname driver, which reads a list of hostnames from the output of a shell command (normally /usr/bin/uuname) and uses this list to match neighboring hostnames.

An example entry for a site that wishes to route to their neighbors for hostnames that may end in .uucp is:
	uuname: transport=uux, driver=uuname;
		cmd=/usr/bin/uuname, domain=uucp
An alternative is a site that wishes to bypass the pathalias router only for explicit target matches, so that the form ``neighbor.UUCP'' will be routed through, as an example, pathalias. This can be done by not specifying a domain, as in:
	uuname:  transport=uux, driver=uuname; cmd=/usr/bin/uuname
The uuname driver also supports the domain, required and try attributes, and all three domain-style attributes can be colon separated lists. See the pathalias driver for more details on these attributes.

In addition, there is a string attribute, statfile which names a file which can be used to determine when the output of the shell command will change. For example, when used with the uuname command this would normally be either /usr/lib/uucp/L.sys or /usr/lib/uucp/Systems depending on whether a site is using HoneyDanBer or stock V7-style UUCP. If a statfile attribute is defined, then smail daemons that expect to deliver multiple messages will cache the output of the shell command. The specified pathname will then be checked at regular intervals to determine if the command should be reissued to refresh the cached information.

The Queryprogram Driver
If no other router driver meets a particular routing requirement, but a shell script or C program can be written which does, the queryprogram driver can be used to access this script or program. This driver runs a program, with arguments, and examines its exit status and standard output for information. The program should return an exit status of zero to indicate a match for the target host, non-zero otherwise. Optionally, this program can write a path and a transport on its standard output to provide additional information. If a path is not returned then a one-hop path to the target host is assumed. The program is always executed as an unprivileged user.

The queryprogram driver supports the domain, required and try attributes, as defined in the description of the pathalias driver. The program and its arguments are described in terms of a cmd attribute which is a string consisting of white-space-separated tokens which are expanded to form a program name and the arguments to pass to that program. The variable $host can be used to obtain the target host string. White space or punctuation from an expansion variable do not delimit arguments. Two additional boolean attributes affect the driver's behavior:

read_path
    If this attribute is enabled, then a path is read as the first white-space delimited field in the first line of output from the program. If no output is produced by the program, or this attribute is not enabled, then a one-hop path to the target host is assumed. A path should consist of a list of hostnames separated by an exclamation point (`!') character.

read_transport
    If this attribute is enabled, then a transport is read as a white-space delimited field from the first line of output from the program. If the read_path attribute is also enabled, then the transport is taken from the second field, otherwise it is taken from the first. If no output was generated by the program, or the field did not exist in the output, then the normal methods for determining the transport are used.

A trivial example of the use of this driver is the router file entry:
	match_bar:
		driver=queryprogram, transport=bar;
		cmd="/bin/test X${lc:host} = Xfoo"
This router will use the program test(1) to determine if the target host is foo. If this is the target host, then it is assumed to be a neighboring host which can be reached over the transport bar.

A more complex example is to create a shell script such as:
	# match_fubar.sh - match hosts on the fubar networks
	case "$1" in
	foo)	echo "foo foo_transport"; exit 0;;
	bar)	echo "foo!bar foo_transport"; exit 0;;
	curds)	echo "curds curds_transport"; exit 0;;
	whey)	echo "curds!whey curds_transport"; exit 0;;
	esac
	exit 1
By setting up a router file entry such as:
	match_fubar:
		driver=queryprogram;
		cmd="/bin/sh $lib_dir/match_fubar.sh ${lc:host}",
		read_path, read_transport
a complete, though not particularly optimal, router is created which can match the hosts foo, bar, curds and whey and cause messages to these hosts to be delivered using one of the transports foo_transport or curds_transport.

The queryprogram driver is not very efficient, as it requires a fork/exec for each host. However, it is a very simple to construct a new router using this driver, so it is useful for prototyping. In general, a new form of routing requirement is most efficiently handled by writing a new router driver.

The Gethostbyname Driver
In a networking environment, hostnames on a network can be matched using this driver, which calls the gethostbyname(3N) library routine. This routine is only available on systems that supply a BSD compatible internet networking library. Driver attributes for this driver include domain, required and try attributes, which are compatible with the pathalias and uuname drivers.

Additional attributes are: Do not match hosts that have a domain component (i.e., that contain a dot). The domain attribute is applied before the only_local_domain attribute, so hosts that have a domain component consisting only of one of the strings listed with the domain attribute can be matched.

gethostbyname will only match a target host completely. The hostname given to the transport will be the host as given by the h_name field of the hostent structure.

NOTE:
    The hostname given to gethostbyname(3N) will be downcased, so that upper-case or mixed-case names can be matched correctly.

The Gethostbyaddr Driver
Also in a network environment, it is useful to be able to specify explicit Internet addresses using a target such as: [192.2.12.3] which is the internet address for the host eek.uts.amdahl.com.

The gethostbyaddr driver matches targets of this form, which is defined by square brackets surrounding only digits and dot characters. The driver then converts this number into a hostname by calling gethostbyaddr(3N) to determine the proper name for the host. If gethostbyaddr fails, then the input domain literal name is given to the transport. This is useful with incomplete host tables.

The gethostbyaddr driver has the following attributes: If set, see if the hostname returned by gethostbyaddr() matches one of the known names for the local host. The name ``localhost'' is counted here as a potential name for the local host. NOTE: This attribute is set by default. If set, then any domain-literal target which does not fit the form of an internet address is considered an error. If not set, then such addresses are merely not matched by the driver.

The Bind Driver
The bind driver uses the Berkeley Internet Name Domain server, named , to resolve target hostnames. It is fully compliant with the RFC974 standard, Mail Routing and the Domain System , and uses MX and WKS records. This router is available only on systems that have a 4.3BSD compatible resolver library. It is highly recommended that this router be used for machines that are on the internet, rather than using the gethostbyname router.

The following attributes vary the behavior of the bind driver: If this boolean attribute is set, then we must be able to connect to the server. If attempts to connect to the server fail, then routing is retried at a later time, on the assumption that the nameserver is only down temporarily. If this attribute is not set, then a failure to connect to the server will cause the router to be ignored. This allows a bind router to be optional based on whether or not the server exists. NOTE: This attribute is set by default. If this boolean attribute is not set, then it is considered an error for an MX resource record to be encountered which points to the local host. If this attribute is set, then such an MX resource record will cause the address not to be matched. The precedence number for the resource record is taken into account here, so that an MX resource record which points to the local host is ignored if there are other records with a lower precedence number. This boolean attribute is passed to the BIND resolve routines as the RES_DEFNAMES flag. If set, then hostnames which do not contain dots will have a default domain appended to them before lookups. For example, this allows for hosts on a local area network to be referenced using the basename of the host rather than requiring the full domain name. NOTE: This attribute is set by default. If this string is set, then it is used as a colon-separated list of domain names. If a hostname ends in any of these domains, then the router will not match the host, and will not result in any queries. This can be set to a list of domains that are known not to exist, such as uucp and bitnet, to prevent expensive lookups which will never be successful. If this boolean attribute is set, then a hostname with only one domain component (i.e., no dots) will not be matched. This should probably be set if defnames is not set, to prevent lookups for uucp hostnames that will not be found by BIND. If this boolean attribute is set, then match a host only if it has an MX record. This is not currently useful on the Internet as a whole, though it does have uses in managing networks disconnected from the Internet, but that use BIND to manage the hostname space. If all hosts that can accept mail have an MX entry pointing to them, then no attempts will made to send mail to other ``hosts,'' such as printers or terminal concentrators. A list of gateways and corresponding domains for explicit routing using the bind processing logic for the gateway address. The string consists of a sequence of lists. Each list consists of strings separated by colons, and the lists are separated by a string consisting of a single `+' character. Each list consists of the name of a gateway, followed by a list of domains that should be routed to that gateway. The gatewayed domains will match either against a complete address, or against the terminating domain of an address. For example:
    gateways = "uknet.ac.uk:uucp:+:\
                earn-relay.ac.uk:bitnet:ie:earn"
In this example, if an address of the form <anything>.uucp is being processed, it will be converted to uknet.ac.uk before any other processing is done. The new name will then be looked up in the DNS and routed accordingly. Thus mail for <anything>.uucp will always be sent to uknet.ac.uk, by whatever route is registered in the DNS for that address. Similarly, mail for the domains bitnet, ie, and earn will be routed to earn-relay.ac.uk. A list of domains, separated by colons, to be tacked onto the end of the address if it isn't found directly in the DNS. For example:
    widen_domains = "cam.ac.uk:ac.uk"
With this setting, an address such as "psy.ox" will first be tried as it stands, then "psy.ox.cam.ac.uk" will be tried, and if that fails, "psy.ox.ac.uk" will be tried.

The following attributes are for use in the UK, where mail routing is complicated by the co-existence of both the Internet and the JANET mail protocols. If this attribute is set, then an address which is matched in the DNS but which does not have any usable MX records because they have been discarded for UK-specific reasons (see below) will be routed to this transport, provided the address ends in `.uk'. The string should be the name of a transport defined in smail's transports configuration file.

    If this attribute is not set, such an address will cause a `nomatch' return, allowing a subsequent router (typically smarthost) to handle the message. If this switch is set, addresses that are sent to the greybook transport are left in world order, otherwise they are inverted into UK order. A list of known gateways which are not to be used for sending SMTP mail within the UK (that is, to addresses that end in `.uk'). For example:
    uk_ignore_gateways = "nsfnet-relay.ac.uk:\
                          sun2.nsfnet-relay.ac.uk:\
                          mhs-relay.ac.uk"
The highest MX precedence value that is acceptable for an address in the UK for SMTP mail. The default value is 999, which disables this option, but sites in the UK should normally set it to 9 in accordance with the established convention that preference values greater than 9 should not be used for intra-UK SMTP mail. If this attribute is set, then when an address cannot be found in the DNS, even after widening with the strings given in the widen_domains attribute, the original address is inverted (e.g. uk.ac.somewhere becomes somewhere.ac.uk) and the whole process is tried again. Inversion does not take place if the address already ends in `.uk'.

All matches found by the bind driver are considered full matches, for the purposes of prioritizing results from different routers. Matches are considered full even in the presence of wildcards in MX records.

A site which exists only on the internet, requiring no other means of routing should have a router file consisting of the entries:
    # match internet address domain literals
    internet_addrs:
    	driver=gethostbyaddr, transport=smtp;
    	fail_if_error
    # match internet hostnames
    internet_hosts:
    	driver=bind, transport=smtp
A site which servers as the internet gateway for some set of hosts should either have a paths file naming the hosts for which it gateways, or should use the local_mx_okay attribute and allow target hostnames to fall through to a router for another network. For example, a UUCP network gateway which gateways for a set of hosts listed int the UUCP map database distributed over USENET could use the following two routers, in order, to handle all of its gateway responsibilities:
    internet_hosts:
    	driver=bind, transport=smtp;
    	local_mx_okay
    uucp_hosts:
    	driver=pathalias, transport=uux;
    	file=/usr/lib/smail/paths
If the defer_no_connect is not used, then it is advisable to include a gethostbyname router to match hostnames. The following sequence of routers will allow the same smail configuration to be used on machines that do have the BIND server and on machines that don't have the server:
    internet_hosts:
    	driver=bind, transport=smtp;
    	-defer_no_connect
    network_hosts:
    	driver=gethostbyname, transport=smtp

The Smarthost Driver
Sometimes it is handy to be able to redirect mail to a host that you don't know about to some other host that has more routing information. This other host is called a smart host, and can be named by using the smarthost driver.

The smarthost driver has the following driver attribute: This define a host or UUCP-style `!'-path path that defines the smart host.

If no transport or method attribute is given for the router file entry, this address will be resent through all the routing drivers. An exception is that an address cannot be sent to the smarthost driver twice, as this would mean that the path to the smarthost was not known.

The global configuration variable auth_domains affects the smarthost router by restricting the set of hostnames that can be matched by the smarthost router to hostnames that are outside of the domains listed in auth_domains.

For example, if the site namei wanted to use amdahl's routing database for mail delivery to non-neighboring sites they could use a router file entry of:
	smart_host: driver=smarthost;  path=amdahl
or	smart_host: transport=uusmtp, driver=smarthost;
		path=amdahl

NOTE:
    At the present time, a transport or method attribute is required, as the software is not yet in place that can rescan the routers in the required ways.

Then, a recipient address of ``Ted.Husted.Jr@walldrug.uucp'' will be rewritten so that the hostname is amdahl and the remaining part of the address is ``Ted.Hustead.Jr@walldrug.uucp.'' Alternately, in the second form for the entry, the transport, uux, would be known immediately and be passed the hostname ``amdahl'' immediately, with a $user value of ``Ted.Hustead.Jr@walldrug.uucp.''

By specifying a UUCP-style `!'-path it is possible to route mail to a smart host that you would not otherwise be able to route to. For example, if the machine glotz wished to use amdahl as its smart host, through its neighboring site namei, it could use:
	smart_host: driver=smarthost; path=namei!amdahl
or	smart_host: transport=demand, driver=smarthost;
		path=namei!amdahl
It is possible to set the path and/or the transport in the config file. This is done by setting the config file attributes smart_path and smart_transport. For example, the config file could contain the following:
	smart_path = amdahl
	smart_transport = uusmtp
Then, if the entry in the router file was:
	smart_host: driver=smarthost
the configuration would be essentially the same as in the second smart_host example above. This makes it possible to share copies of the router file among several machines, with the smart host configuration specific to one machine being set in its private configuration file.

These config file attributes are used only if the path driver attribute is not given in the smart_host entry. If the smart_path attribute from the config file is used, the smart_transport will override a transport or method attribute.

The Rerouter Driver
The rerouter driver is an experimental router driver that can do optimization of UUCP-zone !-paths addresses. For example, given an address of:

    host1!host2!host3!host4!host!user

The rerouter driver could realize that a more efficient path exists to host and rewrite this as:

    host6!host!user

Before you say to yourself how neat this would be and how much of a savings this would be for the world, you must realize that such rerouting is dangerous and should be configured-in only with a great deal of consideration and attention to detail in your rerouting database.

Here are the attributes supported by the rerouter driver: An expansion string defining a file that selects which hosts or domains will be considered candidates for rerouting. If the string, after expansion, does not begin with /, it will be opened relative to the smail library directory. The format of the file is described later in this section. The lookup protocol to use in searching through the database specified by the file attribute. The list of possible lookup protocols for the rerouter driver is the same as for the pathalias driver. A colon-separated list of default domains for hosts in the database. Targets ending in any of these domains will have the domain stripped (incuding a preceding dot) before the database is searched. A target containing only the domain (e.g., just .uucp) will remain unchanged. A colon-separated list of domain names that are must be part of a hostname for that hostname to be considered a candidate for rerouting. If set, then reopen the database for each call to the rerouting driver, and close before each return. This is necessary for systems that would not otherwise have a sufficient number of available file descriptors for all of their routing and directing needs. if set, then if the open of the database file fails, assume an empty file. if set, then if the open fails, try again on a later spool directory queue run. If set, reroute all bang path addresses. The rerouting database isn't used at all in this mode, so even hosts that have an exclusion flag (`-') in the database will be rerouted. Use this only for debugging purposes. Unconditional rerouting is an offense against the net.community! If set, then address containing forms for the local host (within the bounds of the required attributes) are considered candidates for rerouting. The path starting with the component directly following the last occurance of the local hostname is used rerouting. For example, if the local hostname is geminix, then the input path:

        host1!host2!geminix!host!user

    might be rewritten as:

        host4!host!user
If set, a database lookup is done for the target. Otherwise, the reroute database isn't used. This must be set of you intend to set the file attribute to point to a database. This attribute combines with the matchlocal attribute to do limited rerouting that bypasses multiple occurances of the local host, but only for bounce messages (messages generated for returning errors to the originator of a message). This attribute affects only the use of the matchlocal attribute, and has no other affect on the rerouter driver.

The rerouter driver operates only on pure !-path addresses. For such addresses, the !-path is scanned from right to left for hostnames that are considered candidates for rerouting. If such a host is found, the path is truncated to contain everything from that component to the end of the path. In the case of a match resulting from the matchlocal attribute, the matching component is also removed from the path.

Given a truncated path generated by the rerouter driver, the address is passed back into the smail address resolver engine to be rerouted based on the other routers. This goes all the way back to the beginning of the address resolution process, rather than continuing on with the list of routers, as would happen for a non-matching target hostname.

If a database file is used to define candidate hosts for rerouting, the file will be presumed to contain entries consisting of a hostname or a domain name beginning with a period, followed by + or -. For example, the database file might contain:

    .do.main	+
    .bar	+
    .foo.bar	-
    host1.foo.bar	+
    host2	+
    host2.abc	+
    host3	+
    host4	+

If a match is found on the given hostname, then the + or - is used to indicate whether the hostname is a candidate for rerouting. A + indicates that the host is a candidate, a - indicates that the host is not a candidate.

The rules for finding an entry in the database are:

1.  Look for an exact match of the target hostname. If not found, and the domain begins with a dot, look for a match without the dot.

2.  If that fails, strip the first component of the domain, leaving the initial dot on the second component. Look for a match on the resulting name. Repeat this step until a match is found or no components remain.

This lookup algorithm, together with the + or - field can be used to enable rerouting for all but a certain subset of hosts within a domain.

  General recommendations
While rerouting can be useful, and can improve the flow of mail through the UUCP zone, it can be disastrous if done wrong. Here are two situations where it can be useful to reroute mail:

1.  If your site is on the Internet, and it is a backbone for a domain of UUCP sites that are connected to your site, then your site might have access to routing informations that isn't available to the UUCP sites (MX-records etc.). Using shortcuts over the internet instead of sending the mail along the original slow and maybe expensive (telephone charges) path can be a major advantage.

2.  If one or more links that in your direct neighbourhood (one or two hops away) have changed and the new UUCP maps haven't yet propagated widely enough to make other sites aware of these changes, you could use rerouting to temporarely correct the incoming bang paths that were generated from the old maps.

However, before you enable rerouting you should make sure that your routing databases are really accurate. It's not enough that you install the posted USENET maps automatically. These maps are notoriously inaccurate, and often contain very unrealistic link costs, resulting in non-optimal routes. Therefore, it is necessary to check all routes that might be used for rerouting line by line whenever it is rebuilt from the maps.

If you can't or don't want to do this, don't use rerouting! Or at least only for sites in your direct neighbourhood. Rerouting with a poorly maintained routing database is a disservice to the net! The simplest way to setup rerouting is to limit the set of hosts that you use for rerouting and ensure that the routes to all of those hosts are stable and accurate. Making a separate paths file-based router is the simplest way of ensuring that stable paths are used.

Also, if you think that you have the administrative resources for rerouting, do so only when you are willing to keep in touch with the maintainers of other rerouting sites in your area. Mail loops between two rerouting sites are a serious problem that can be reduced only by discussing changes you want to make to your routing in advance.

So in short, folks, don't use rerouting if it isn't absolutely necessary. Please don't use it as a means to inflate your ego. Instead, maintaining a rerouting host is a responsible task that needs lots of time and determination. Please restrain yourself, for the sake of fast and flawless mail delivery.

  Hostname non-uniqueness
One more point, which is actually an important one, is that hostnames within UUCP-zone are not always unique. Just because you recognize a hostname on the end of path does not mean that it is the host that you think it is. To avoid conflicts arrising from non-unique names it is best to avoid rerouting for hostnames that are not qualified within a domain.

The only safe way to reroute an address is to reroute from left to right rather than right to left, and to stop as soon as a host is found which is not a rerouting candidate. However, such a policy greatly limits the usefulness of rerouting or at least it greatly increases the number of entries in your rerouting database that are necessary for rerouting to be useful.

THE TRANSPORT DRIVERS
This section details the usage and driver-specific attributes for all of the transport drivers distributed with smail. See the section THE TRANSPORT FILE for more information on transports.

The Pipe Driver
The pipe driver is the most general form of transport. Its job is to send mail messages to another program, such as uux(1) or sh(1).

The driver attributes for the pipe driver are: The program to be run and the arguments to be passed. This is string expanded. To handle multiple addresses being given to a transport, the use of $( and $) can be used to bracket a section of the command string which is to be repeated for each address given to the transport. It is a configuration error for string expansion to fail. Generally, only child failures from the signal SIGTERM are reattempted at a later time. If this is set, then retries are performed at a later time if the exit code is non-zero, or if the write failed on the pipe. This is useful for treating errors from UUCP as configuration or as temporary filespace problems. The name of the group to setgid(2) to within the child process. Useful only if the mailer is running as root. If set, the exit status of the child process is ignored. If this is not set, an exit value other than 0 is noted and mail is sent to the postmaster stating this. If set, write errors are ignored. This is useful for running programs that may not actually read their standard input. If this is not set, a write error will cause mail to be returned to the sender. The stdout and stderr of a command are logged and returned to the sender in case of problems. The current implementation is not very good as it actually returns the logs for all such transports in the event that any transports fail. This attribute is on by default. Stuff the environment with data taken from the parent of the input address, rather than the input address itself. This is useful for the transport specifically named pipe which is used by smail for delivery to shell-command addresses. Here the recipient address stored into the environment will then be the address that produced the shell-command address, rather than the shell-command address itself. If set, the child process' uid is taken from the real uid at the time the message was read by smail. This does not affect the group id for the child. This overrides the uid obtained from the pipe_as_user attribute. Obtain a uid and, if `group' attribute is not given, a gid associated with the address (such as the user for a .forward file). Then set these via setuid(2) and setgid(2) in the child process. NOTE: This attribute is on by default. file creation mask for the child process. The name of the user to setuid(2) to within the child process. Useful only if the mailer is running as root.

The environment of the child process is entirely initialized and loaded with variables which may be useful in shell scripts or intelligent mail processing programs. Exactly one environment variable is passed through from the environment handed to the smail program: the TZ variable defining the timezone. The following portion of the environment is independent of the recipient addresses:
BASENAME	the basename for the spool file
GRADE	the grade character
MESSAGE_ID	the message ID as assigned by smail
PATH	``/bin:/usr/bin''
PRIMARY_NAME	the official name for the host
SENDER	the sender address
SHELL	``/bin/sh''
SPOOL_FILE	the complete name for the spool file
UUCP_NAME	the name for the host on the uucp network
VISIBLE_NAME	the name for the host used in addresses
The rest of the environment is loaded from the input address, or from the parent of the input address:

ADDR
    The recipient address (or one of the recipient addresses, if more than one is given to the driver).

HOME
    The home directory (or one of home directories, if more than one recipient address is given to the driver). If no home directory is associated with an address, ``/'' is used.

HOST
    The recipient hostname (or one of the recipient hosts, if more than one host is given to the driver).

USER, and LOGNAME
    These two variables are loaded with the name of a user on the local host, if one is found with some association to the address.

Examples of the use of the pipe driver are:
	# transport used for delivery to shell-command addresses
	pipe:	from, local, return_path, unix_from_hack,
		driver=pipe;
		cmd="/bin/sh -c $user",
		pipe_as_user, ignore_status,
		ignore_write_errors, parent_env,
		-log_output
	# delivery to a remote rmail(8) program using uux(1)
	uux:	max_addrs=5, max_chars=200, from, received,
		driver=pipe;
		cmd="/usr/bin/uux - -r -g$grade $host!rmail
			$((${strip:user})$)",  # see ``String expansion'' above
		pipe_as_sender

The Appendfile Driver
The appendfile driver creates or appends to files. It can either write to a filename derived from the recipient address, or it write a unique file into a directory. This latter capability can be used to implement a primitive output queue for some purposes.

The driver-specific attributes are: Get the uid and, perhaps, the gid from the user id and group id associated with the address. For example, the user associated with a forward file might be used. This attribute is on by default. If set, then verify the permissions on a complete path for a file or dir attribute. This requires that all directories leading to a file must be searchable by the appending user (see the user, group and append_as_user attributes). Under System V, this requires a stat(2) call for each directory in the path, and is thus somewhat expensive. Reject an address if the $user would contain a `/'. This prevents a $user expansion from accessing a different directory. Defines a directory in which to write unique files. Files written to this directory always begin with the letter `q', while temporary files used in the creation process begin with ``temp.'' This string is expanded similarly to the file attribute. It is a configuration error for this string expansion to fail. If set the value for $user value is string expanded before the value for the file or dir attribute is expanded. This is useful if a local-form address may require `~' or `$' expansions. Defines a file to append messages to. This string is expanded, and the variables $user and $host are set from the recipient address. It is a configuration error for this string expansion to fail. become this group. Similar to the user attribute. When creating a file, creat(2) it with this access mode. The default is 0666. Notify the COMSAT daemon of the message delivery, so that users can be notified that they received mail. This has no effect if your system does not support the COMSAT daemon. This should be used for delivery to user mailbox files. This prefix is inserted in the file before the message. This string is expanded, with $user and $host being available from the recipient address. It is a configuration error for this string expansion to fail. This suffix is appended to the file after the message. This string is expanded, with $user and $host being available from the recipient address. It is a configuration error for this string expansion to fail. This become this user (effectively at least) when opening or creating the file. Access permissions are checked relative to this user, and the user will own the file if it did not previously exist.

To better understand the use of some of these attributes, consider the transport file entry:
	file:	driver=appendfile, from, return_path, local;
		file=$user, suffix="\n", check_path,
		expand_user, append_as_user, mode=0664
This transport will be called when a file address is produced by a director. Such addresses should be expanded, because they may require `~' expansions. Also, to keep standard many user agents happy, an extra newline is inserted after each message. The append_as_user attribute is set to ensure that addresses produced from, say, a forward file are only created or appended to if the associated user has permissions to do so. Because these filenames can be arbitrary, check_path is set to make sure that an otherwise inaccessible directory is not written to.

When given an address of ``~/Incoming,'' with an associated home directory of ``/u/joe-user'' and an associated user of joe-user, the following steps occur:

a.  The $user variable is expanded to ``/u/joe-user/Incoming.''

b.  The file attribute is also expanded to ``/u/joe-user/Incoming.''

c.  The directories /, /u and /u/joe-user are checked for accessibility by the user joe-user. If any of these is not searchable, then delivery fails.

d.  The file /u/joe-user/Incoming is opened for append access. If it does not exist, it is created, will be owned by joe-user and will have mode 0664. Creation will fail if joe-user cannot write the directory.

e.  The message is written with a local-form ``From<space>'' line.

f.  An extra newline is appended to the file, after the message.

NOTE:
    smail will follow the local conventions on locking protocols for mailbox files, which may involve creating a .lock file or using a file lock system call, such as lockf(3) under System V of flock(2) under BSD.

Next, lets examine:
	local:	driver=appendfile, local, from, return_path;
		file=/usr/spool/mail/$user, append_as_user,
		check_user, mode=0600, notify_comsat
In this example, the $user value is not expanded before expanding the file attribute. Also, just to make sure, $user is verified to not contain a `/'. Given an input address of ``jane-doe,'' associated with the user jane-doe, mail will be appended to the file ``/usr/spool/mail/jane-doe.'' If it did not previously exist, it will be owned by jane-doe and will have a mode of 0600.

The TCPSMTP Driver
Simple support exists in smail for delivery using SMTP over TCP/IP, for systems that have BSD compatible networking. It is intended that eventually a complete backend will exist to handle SMTP in a more efficient manner, though in the mean time a built-in SMTP transport driver is available.

The smtp driver can be used for delivery of any number of addresses to one remote host, where the remote host can be specified either in form of a hostname known by the networking software or by an internet number in square brackets, such as [192.2.12.142]. For example, the routing drivers gethostbyaddr and gethostbyname are suitable for matching addresses to be delivered using the SMTP driver.

The attributes for the tcpsmtp driver are: This defines the response timeout for oerations that are assumed to be short, such as protocol startup and protocol exit. This can use suffix letters of `s', `m', `h', and `d' to mean seconds, minutes, hours or days, with no suffix signifying seconds. Times can be added through direct concatenation. For example, the value `5m30s' signifies 5 minutes and 30 seconds. The default value is 5 minutes. This defines the response timeout for long operations, i.e., those that are not short. Suffix letters can be used in the same manner as with short_timeout. The default value is 2 hours. This attribute identifies a TCP/IP port number, either directly as a number, or as a name to be searched for in the /etc/services file. This port number will be used in connecting to the remote host. The default is smtp. Use DNS resolution, if supported, to locate and use MX and A records associated with the target host; without this option, the gethostbyname() function is used to locate the address to use for delivery. If the target host was matched with the bind router driver, then MX and A records found by the bind router will be used independent of the use_bind attribute.

defer_no_connect, local_mx_okay, defnames, ignore_domains, domain_required, mx_only

    If use_bind is specified, these attributes vary the behavior of the tcpsmtp transport's DNS resolution. See the documentation for the bind router for an explanation of these attributes.

The smtp driver attempts to connect immediately and deliver a single message. If access to the remote host is currently not possible, the driver will tell smail that delivery should be attempted at a later time.

An example of the use of the smtp driver is the entry:
	# deliver using SMTP over TCP/IP to the remote host
	tcpsmtp: -max_chars, -max_addrs, driver=smtp
If your site is on the Internet and gateways from the UUCP zone, it may be reasonable to set the strict attribute. Otherwise, this is probably not a good idea.

If the local attribute is set (see the generic transport attributes), then mail will be transmitted in a form that contains little reference to the transmitting host. This can be used within a local network to make all mail transmitted within the network look like local mail (i.e., local addresses will not be qualified with the domain name). This is often convenient in environments that use a central host for processing all mailing lists and user addresses, but where mail can originate and be delivered anywhere in the network, and where user names are consistent throughout the network.

When mail is transmitted outside of the local network, an smtp transport with the local attribute turned off will qualify any mail sent from anywhere inside the network.

The SMTP transport is also affected by the inet and uucp generic transport attributes. If inet is set, then sender and recipient addresses transmitted in the protocol envelope will strictly conform to the RFC821 and RFC1123 protocol specifications. However, route-addr addresses may be generated, despite the recommendations of RFC1123 against the practice. Note that networks connected completely by domain name servers will not result in generation of route-addr addresses, although they will be honored if received.

If the uucp transport attribute is set, then sender and recipient addresses will conform to the envelope specifications of RFC976, and will thus use !-style routes. Addresses transmitted to the remote host will consist only of ! and % operators. % operators will never be generated, but may be included if they were present in the original sender or recipient addresses.

If neither the uucp nor the inet attributes are specified, then an intermediate form will be used that nearly eliminates route-addr addresses. This form uses RFC976 !-style addresses when routing is necessary, but otherwise stays within the formal SMTP specification.

The smtp driver always sets the crlf and dots transport attributes.

DEFAULT CONFIGURATION

NOTE:
    A transports file, unlike routers and directors files, does not replace all compiled-in transports. Rather, entries in the transports file override existing entries of the same name, or add new entries. Thus, if you wish to add new transport definitions, you need only create a transports file containing the new defintion, and do not need to duplicate all of the compiled-in entries.

The default internal configuration is defined in the source files config.h and default.c. The default director configuration uses:

aliases
    an alias database stored as an ASCII text file in /usr/lib/aliases

dotforward
    forward files stored in user home directories in the file .forward

forwardto
    forwarding information stored in user mailbox files preceded by the string ``Forward to ''

user
    matches local users with delivery using the local transport

real_user
    matches local users with a prefix of ``real-'' with delivery (bypassing forwarding) using the local transport

lists
    mailing lists stored in the directory /var/lib/smail/lists/

smart_user
    a smart-user director may also be defined.

The default router configuration uses:

inet_addrs
    match domain literals forming IP internet addresses, deliver with the transport smtp; configured in if BSD style internet networking is available

inet_hosts
    call gethostbyname to match hosts on an IP network, deliver with the transport smtp; configured in if BSD style internet networking is available

paths
    a pathalias database stored as a sorted ASCII file in /var/lib/smail/paths

uucp_neighbors
    resolution of neighboring hosts on a UUCP network by calling the program uuname (1)

smart_host
    a smarthost router may also be defined.

The default transport configuration defines:

local
    deliver mail to local users. Usually, delivery is accomplished by writing directly to user mailbox files (either in /usr/mail or in /usr/spool/mail). Alternately, mail may be delivered by calling a program, such as /bin/mail or /bin/lmail to perform delivery using system-dependent conventions.

pipe
    deliver mail to shell command addresses. Shell-command addresses begin with a pipe character (|). The pipe character is stripped from the address and the remainder of the address is passed as a command to /bin/sh. Shell-command addresses can be generated by mailing lists or forwarding files, but cannot be specified as input to smail.

file
    deliver mail to file addresses. File addresses begin with a / or ~ character. If a file address begins with the ~ character followed by the name of a local user, then the ~ and username is replaced by the user's home directory. If a file address begins with ~/, then the ~/ sequence is replaced by a home directory that is appropriate to the context of the address. Normally, ~/ is used within the context of addresses specified in a user's .forward file.

uux invoke uux to deliver mail to a remote rmail program. The -r option is given to uux to prevent an immediate poll.

demand
    this is similar to the uux transport, except that the -r is not supplied. This will request that UUCP attempt to poll the remote site immediately.

uusmtp
demand_uusmtp
    invoke uux to deliver mail to a remote rsmtp program (supplied in the Smail3.1 distribution). The transmitted message will be encapsulated in an envelope of SMTP directives, with addresses passed in through the SMTP envelope rather than in the argument list to uux. This works better than the standard rmail protocol, because quoted addresses can pass through unscathed, and because no limits are given on the number of addresses that can be given in a single transfer. This last point can significantly reduce the number of uux transfers needed for large mailing lists, since the normal method of using rmail is limited by uux's internal limit of (usually) 300 characters of worth of arguments.

    Note that the uusmtp transports are not likely to be useful unless both the receiving host also uses Smail 3.1.

    The uusmtp transport passes the -r option to uux, while the demand_uusmtp transport does not. Also, the uucp generic transport attribute is used by uusmtp and demand_uusmtp to transfer addresses in accordance with the RFC976 specification. This violates the RFC821 and RFC1123 specifications, but is none-the-less useful between sites operating in the UUCP zone.

inet_uusmtp
inet_demand_uusmtp
    These transports are identical to the uusmtp and demand_uusmtp transports, except that the inet transport attribute is enabled, and the uucp attribute is disabled. This causes mail addresses to be transferred in accordance with the SMTP specification. If routing is required to reach a destination, then route-addr addresses are generated (e.g., <@host1,@host2:user@destination>).

smtp
uucp_zone_smtp
inet_zone_smtp
    deliver mail to a remote host by using the SMTP protocol over a TCP/IP connection. If used in conjunction with the bind router, MX records will be handled in accordance with RFC974 and the RFC1123 updates to RFC974.

    The uucp_zone_smtp attribute has the uucp transport attribute set, causing transferred addresses to use !-style addresses, as specified in RFC976. This can often be useful when using SMTP within the UUCP zone, but is otherwise inappropriate.

    The inet_zone_smtp attribute has the inet transport attribute set, causing transferred addresses to conform to the RFC821 and RFC1123 specifications for SMTP. This is necessary for correct operation with arbitrary nodes on the Internet. Both the uucp_zone_smtp and inet_zone_smtp attributes will handle generated routes (from paths files) correctly between nodes running Smail3.1. The inet_zone_smtp transport will use route-addr addresses for routing despite RFC1123's recommendations against such a practice. However, generated routes should never be necessary on the Internet.

    The smtp transport is identical to either the uucp_zone_smtp transport or the inet_zone_smtp transport, depending upon local configuration information specified when the smail program is compiled. This depends upon the setting of the UUCP_ZONE attribute in the conf/EDITME file.

local_uux
local_demand
local_uusmtp
local_demand_uusmtp
local_smtp
    These transports are identical to the uux, demand, uusmtp, demand_uusmtp, and smtp transports, except that they have the local_xform generic transport attribute enabled, and the uucp and inet attributes disabled. This causes mail to be transferred to the remote site as if the mail were local to the remote site. This is useful within closely coordinated networks where usernames and central mailing lists are kept consistent or are processed by central nodes.

FILES
The following files and directories are from a typical smail configuration:

/var/lib/smail/config
    Optional general smail configuration. This file can override compiled-in configuration.

/var/lib/smail/transports
    Optional configuration for smail transports; i.e., configured methods of mail delivery. This file replaces the compiled-in transport configuration.

/var/lib/smail/directors
    Optional configuration for smail directors, i.e., configured methods for resolving local addresses. This file replaces the compiled-in director configuration.

/var/lib/smail/routers
    Optional configuration for smail routers, i.e., configured methods for resolving or routing to remote hosts. This file replaces the compiled-in router configuration.

/var/lib/smail/aliases
    A file of aliases for local addresses.

/var/lib/smail/paths
    A file of paths to remote hosts.

/var/lib/smail/lists/
    A directory of mailing list files.

~/.forward
    Lists of forwarding addresses for local users.

/var/spool/smail
    The top of the spool directory hierarchy.

/var/spool/smail/input
    The directory containing messages to be processed and delivered.

/var/spool/smail/msglog
    A directory of transaction logs for individual messages.

/var/spool/smail/lock
    A directory used in smail input spool files.

/var/spool/smail/log/logfile
    A log of smail transactions.

/var/spool/smail/log/paniclog
    A log of configuration or system errors encountered by smail.

/var/spool/smail/error
    Messages that failed due to a small set of fatal error such as a configuration error are placed in this directory. Currently the site administrator must move these back into /var/spool/smail/input when the error condition is resolved.

/var/spool/mail
    The directory for user mailbox files.

SEE ALSO
binmail(1), mailx(1) under System V, Mail(1) under BSD, resolver(3), named(8), pathto(1), smail(8).
Smail Administration and Installation Guide.
DARPA Internet Requests for Comments RFC821, RFC822, RFC974, RFC976, and RFC1123.

BUGS
Colons cannot be included in the value of a list element.

There should be a way of specifying that different errors encountered by smail should result in different actions (i.e., mailing a message to the postmaster, storing a detailed error message in a file).

COPYRIGHT
Copyright(C)1987, 1988 Ronald S. Karr and Landon Curt Noll
Copyright(C)1992 Ronald S. Karr
See a file COPYING, distributed with the source code, or type smail -bc for distribution rights and restrictions associated with this software.