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Re: Mail delivery from Postfix to remote IMAP



At Mon, 22 Apr 2024 19:39:05 +0200, Rhialto <rhialto%falu.nl@localhost> wrote:
Subject: Re: Mail delivery from Postfix to remote IMAP
>
> On Mon 22 Apr 2024 at 19:29:13 +0200, Hauke Fath (SPG) wrote:
> > You would have to have a local delivery
> > agent that (working with stored user credentials) also acts as an IMAP
> > _client_. Interesting concept...
>
> I'd expect some little program already exists that, say, takes a mail
> message on stdin and puts it in some configured imap mailbox... but I
> haven't found one yet. Then I could just use an alias:
>
> user%isp.tld@localhost:	"|imap-delivery user:password%imap.isp.tld@localhost"

That's what a local delivery agent does, effectively, but without
needing the each user's credentials.

Local delivery agents work on a different premise.  The LDA uses its own
master key, so to speak, to authenticate and authorize the MTA to do
delivery to _any_ _local_ mailbox.

I don't know the specifics of Dovecot, but in the Cyrus IMAP server it's
called "lmtpd", and it uses the LMTP protocol, and it uses (or can use)
LMTP AUTH to authenticate the MTA, and it can be configured to listen
either locally on a UNIX (filesystem) socket, or on an internet socket
(IP:port).

However no mailbox provider in their right mind would ever allow any
third party to have LMTP access to their IMAP server!

The whole point of allowing a network connection to LMTP is so that you
can have a farm of SMTP servers all accepting incoming mail and
delivering to one IMAP server.  I once maintained a system with a half
dozen incoming SMTP servers all feeding one big IMAP server.

SMTP goes between unaffiliated systems.  LMTP is "local" to one .

There are programs that can mirror IMAP mailboxes between IMAP servers,
(e.g. mail/isync) but I think that's a different use case than yours.


--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

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