Subject: RE: Is there are replacement for 'UIDL'?
From: Paul Smith <[email-masked]>
To: "Jeff Stephenson" <[email-masked]>, <[email-masked]>
Date: Wed, 20 Feb 2002 10:22:23 +0000
List-Id: <ietf-pop3ext.imc.org>

>It does sound like a waffle.  If they assign an invarient unique ID to
>each message and return it as the UID of that message, then the UID of a
>message should never change.  If they admit to the UID changing, then
>they either (1) don't do what they say they do or (2) have a bug.
>Besides, once a message is in their system how do they explain their
>claim that the forwarder is somehow responsible for the changed UID?
>*They* are now in control of the message!

Thanks for the confirmation. It confirms what I thought.

Paul				VPOP3 - Internet Email Server/Gateway
[email-masked]			http://www.pscs.co.uk/

Date: Tue, 19 Feb 2002 15:51:48 -0800
To: Paul Smith <[email-masked]>, [email-masked]
From: Laurence Lundblade <[email-masked]>
Subject: Re: Is there are replacement for 'UIDL'?
Sender: [email-masked]

This Statement

>Basically, if you send their server a 'UIDL' command it gives you a set of 
>IDs for the messages, then if you ask a few hours later, it'll give you a 
>totally different set of IDs for the same messages. As far as I am 
>concerned this is a breach of the relevant bits of RFC 1939.

is contradictory with this

>  instead, their own Unique Message ID [which does persist across sessions].

which is it?

There's lots of POP servers that don't put any UIDL header into to the 
message header/body you get with a RETR and that's certainly OK. It would 
even be legal (but not nice) to add UIDL headers that have different or 
varying UIDL values than those returned by the UIDL command.

LL

content-class: urn:content-classes:message
Subject: RE: Is there are replacement for 'UIDL'?
Date: Tue, 19 Feb 2002 15:31:29 -0800
From: "Jeff Stephenson" <[email-masked]>
To: "Paul Smith" <[email-masked]>, <[email-masked]>
Sender: [email-masked]

> -----Original Message-----
> From: Paul Smith [mailto:[email-masked]] 
> Sent: Tuesday, February 19, 2002 2:31 PM

> Basically, if you send their server a 'UIDL' command it gives 
> you a set of IDs for the messages, then if you ask a few hours later, 
> it'll give you a totally different set of IDs for the same messages.
> As far as I am concerned this is a breach of the relevant bits of
> RFC 1939.

This is indeed bad - the UID for a message should not change.

> ... they say that their server does not add a UIDL AT 
> ALL to any messages on their servers, they are using, 
> instead, their own Unique Message ID [which does persist across
> sessions].

That's fine - there's nothing that says that the UID has to be stored
*on* the message, as long as the same UID is returned each time you ask.
If you're storing messages in a database, you might use the primary key
of the message in the DB as it's UID, for example.

> ... <they> blame BTWebworld [the domain-forwarding source of most of
my mail] 
> for ?somehow attaching changeable UIDL's which are confusing VPOP3
[our 
> mail software].

I have seen an X-UIDL header added to mail, which can lead to some real
problems - in particular, if a server accepts that as the UID of the
message, you can send it multiple different messages with the same
X-UIDL header and end up with multiple messages with the same UID on the
server.
 
> Is there anything I've missed, or is it just waffle from an ISP which 
> doesn't know what it's talking about?

It does sound like a waffle.  If they assign an invarient unique ID to
each message and return it as the UID of that message, then the UID of a
message should never change.  If they admit to the UID changing, then
they either (1) don't do what they say they do or (2) have a bug.
Besides, once a message is in their system how do they explain their
claim that the forwarder is somehow responsible for the changed UID?
*They* are now in control of the message!
 
-- jeff

Date: Tue, 19 Feb 2002 22:31:12 +0000
To: [email-masked]
From: Paul Smith <[email-masked]>
Subject: Is there are replacement for 'UIDL'?
Sender: [email-masked]

I've just had an email from one of our users, which they've been sent by 
their ISP (British Telecom) which looks to me like total baloney (which 
wouldn't be unusual), but I just want to check that there's not something 
I've missed...

Anyone out there want to read through it, and tell me that I'm correct, or 
that I've missed something?

Basically, if you send their server a 'UIDL' command it gives you a set of 
IDs for the messages, then if you ask a few hours later, it'll give you a 
totally different set of IDs for the same messages. As far as I am 
concerned this is a breach of the relevant bits of RFC 1939.

Their response was:

BTInternet as was, now BTOpenworld, whose server actually holds my "real" 
mailbox acknowledge that changed UIDL's can be demonstrated [now with 
increasing frequency] BUT they say that their server does not add a UIDL AT 
ALL to any messages on their servers, they are using, instead, their own 
Unique Message ID [which does persist across sessions]. They say that this 
is acceptable under RFC POP3 supplemental extension rules and blame 
BTWebworld [the domain-forwarding source of most of my mail] for ?somehow 
attaching changeable UIDL's which are confusing VPOP3 [our mail software].

They seem to be saying that this 'Unique Message ID' is a replacement to 
the UIDL which they claim not to add to messages, but which their servers 
WILL give you if you send a UIDL command. I don't know what these 'RFC POP3 
supplemental extension rules' are that they're talking about.

The only thing I can think of which they could mean by 'Unique Message ID' 
is the 'Message-Id:' header line which is normally added by the message 
SENDER, not POP3 server, and which isn't *guaranteed* unique as a UIDL is. 
Also, it's not generally a usable replacement for UIDL since there's no 
quick way of getting it.

Is there anything I've missed, or is it just waffle from an ISP which 
doesn't know what it's talking about?

I don't see what's hard about assigning a constant UIDL to each message. 
And if they really find it as difficult as they seem to, surely they should 
simply not implement the UIDL command at all - after all it's optional.

Paul				VPOP3 - Internet Email Server/Gateway
[email-masked]			http://www.pscs.co.uk/