On 10 Apr 2013, at 22:22, Timo Sirainen wrote:
GMail's submission server saves all the submitted mails to the
sender's Sent mailbox. After this most IMAP clients with their default
configuration will again save the same mail to the Sent mailbox. I'm
not sure if GMail removes one of them as a duplicate or not. I've been
considering doing a similar feature to Dovecot (it will most likely
have a proxying submission server in near future), but it would be
nice to tell the SMTP clients that this auto-saving is happening, so
they could skip the IMAP APPEND part with default configuration.
Yes, GMail suppresses duplicate messages across the entire store,
apparently solely by use of the Message-ID field, with very interesting
results (including, for example, that one never receives one's own
postings to mailing lists).
Just off the top of my head, I can't see how an SMTP extension would
serve much more than an advisory purpose; either the client understands
the advertised extension and reacts appropriately, or it does not and
then you must process the duplicate received via IMAP yourself. The
SMTP server could, I suppose, internally relay client information to the
IMAP server, but then you're back to the inherent difficulties of the
BURL solution, because the client must explicitly request special
processing for the SMTP server. For this to be simple and controlled by
the client, the information is from server to client, so you would have
to handle the existing "Client duplicates" case regardless. This is
still fine, I suppose, because it costs less for you to discard a
duplicate than it does for a client to retransmit it. Still a bit
unclean, though. :-)
Cheers,
Sabahattin
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