I wonder if it is worthwhile noting a particular kind of non-symmetry
that is common today. Most people run SMTP on their local machine in
order to send messages, but they do not run SMTP to receive messages;
that is done by a remote server, and the user runs a different
protocol (a Mail Retrieval Client?) to fetch the mail. That means
that and OPES server that is closest to the user will probably be
acting as an SMTP relay, while that same server will be an SMTP
endpoint for messages destined to that user. Hope that's clear :-)
Parts of the document are difficult to understand, particularly
the part about referring to earlier commands. What is that about?
Some of the content adaptation use cases seem at odds with the earlier
part of the document that say that these are part of the "mail
delivery agent" which is NOT part of the MTA. So I'd have expected
those use cases to be out-of-scope. What am I misunderstanding?
I can see "response modification" use cases that attempt to
deal with "recipient unknown", for example. It would be a way
of implementing a "universal identity" on a incremental basis.
If delivery fails, you consult the universal identity for
an alternative delivery method. Yes, the MDA or the MUA could
do it, but it's a nice "in-the-network" kind of service.
Yes, I think that operating on the DATA portion fits into the
architecture without the need for special consideration.
Hilarie