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Re: [ietf-smtp] Submission DATA reply to indicate auto-save

2013-04-10 18:44:47
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. :-)

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