On 3 Sep 2011, at 14:39, Dave CROCKER <dhc(_at_)dcrocker(_dot_)net> wrote:
I don't know why RFC 5321 fails to mention ATRN, since it as an enhancement
ATRN is supposed to be used on the ODMR port, not port 25. The client and
server software tends to be separate from normal SMTP implementations.
Here's the essential bit: Occasional connectivity fits into the Internet
mail model only as a last-hop, receive-side issue. There must be an
always-connected server working on behalf of the sometimes-connected receiver
and holding mail for it. Hence, use of ODMR is a 'local' matter. Do not
expect random, remote servers to participate.
Demon Internet in the UK was unusual in using SMTP to deliver mail to its
users. The radius servers kicked off a couple of processed when a user dialled
in: first, set up he routing for the user's static IP address, and second, kick
off a queue runner for that user's mail. It is not safe to do this kind of mail
delivery without static IP addresses! The MTA was MMDF (Demon started out as a
SCO shop but was all BSD and Solaris when I was there) and the queue was split
with a directory per user so delivery was fast. The POP service was added later.
ODMR is better than POP in retaining the message envelope and not having the
"keep mail on server" loophole.
f.anthony.n.finch <dot(_at_)dotat(_dot_)at> http://dotat.at/