Subject: [saag] will email key discovery be done by MUAs or MTAs/MSAs? (was: IETF 93 Agenda Request - Key Discovery)

From: Keith Moore <[email-masked]>
Date: Fri, 24 Jul 2015 17:03:59 -0400

Matt Miller wrote:
> I think key discovery will be used far far more by MUAs than MTAs or MSAs.

As much as I would prefer that all MUAs implement key discovery and 
encryption, I actually suspect that key discovery will be used more 
frequently by MSAs than by MUAs, at least in the near term.   Part of 
the reason for this is that it's much easier to deploy:   MSAs are 
better maintained, less diverse, and easier to upgrade than MUAs.   
Another part of the reason is that various enterprises have legal or 
other requirements for logging of outgoing mail, which is easier to 
implement if encryption (and thus key lookup) are done in the MSA.

MUAs should of course be capable of doing key lookup and encryption, but 
some enterprise MSAs might be configured to refuse to deliver encrypted 
messages.

But, really, the effort of implementing client query code for either 
AQRY or webfinger (regardless of whether done on an MSA or MUA) is 
minimal.   That's not an important distinction between the two. The 
important distinctions are things like:  how to keep the interpretation 
of an address consistent with that mail domain's interpretation of the 
address, how to deal with things like mail forwarding and aliasing, how 
to verify that the information obtained is authentic, how to optimize 
deployability, etc.

Keith