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Forgive me if I'm missing something obvious here..... but why do most linux server distros come with both Dovecot AND Postfix (or sendmail)? As far as I'm aware all three of them are Mail Transfer Agents, with Dovecot having a 'secondary' function of being a Mail Delivery Agent...

Is Dovecot just not a very good MTA? Or is there some other reason why you'd want to use a combination of the above instead of a single program that seemingly does everything?

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  • counter question: why does linux distros have so much editors like emacs, vi, nano,...? Answer: This is called "freedome of choice"! – deagh Sep 7 '14 at 8:59
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    What makes you think that Dovecot is an MTA? – andol Sep 7 '14 at 9:06
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MTA is the service that route messages from one region to another. You drop the letter in the public submission box and MTA pass it to the city where recipient live. Then local delivery agent (LDA) delivers letter to the recipient's residence. And then recipient fetch the letter from his personal POP/IMAP mailbox and read it with MUA.

Email simply resembles old good classic mail service. When you get the similarity, you'll get the meaning of each service.

May be that helps

MTA:

MTA

LDA:

LDA

POP/IMAP:

POP/IMAP

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    One of the most awesome answers on serverfault evar!!! – Michael Moser Apr 27 '17 at 5:32
  • The MDA should have been a PO Box – Fotios Basagiannis Aug 2 '17 at 23:57
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"Note that Dovecot is NOT responsible for receiving mail from other servers. Dovecot only handles e-mail (a) messages coming out of the local message store, going out to IMAP and POP3 clients, and
(b) messages which have already been received by the MTA and are to be stored into the local message store."

(Taken from http://wiki2.dovecot.org/MailServerOverview)

So there was something obvious I missed; Wikipedia can be misleading:

"Dovecot also includes a Mail delivery agent (called Local delivery agent in Dovecot’s documentation), with optional Sieve filtering support."

Also includes an MDA... Dovecot is, in fact, an MDA.

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    MDA functionality is an option for dovecot. As well as AUTH-server and autoresponder. Primary role of dovecot is THE POP/IMAP server. – Kondybas Sep 7 '14 at 20:32
  • So the POP/IMAP server functionality doesn't classify it as an MDA? How does this differ from an MTA that 'sends' POP/IMAP mail? – Nom Sep 8 '14 at 8:56
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    In fact dovecot's MDA deliver is the standalone utility that knows nothing about POP/IMAP. Dovecot itself can't deliver messages but share config with deliver - that make configuration way easier. – Kondybas Sep 8 '14 at 10:44
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    Seems you confused with meaning of delivery. MTA, MDA and POP/IMAP all performs some kind of delivery. Messages are routed between MTAs. MTAs knows about domains and know which MTA is an MX for each domain. When MTA see that message is for domain whos MX it is, message is passed to the MDA. MDA knows nothing about domains and MX but knows about users of local domain and where their mailboxes are located. MDA delivers message to the local storage into the user's mailbox. And then POP/IMAP allows to access mailbox and to read/fetch messages. Only MDA part is called delivery. – Kondybas Sep 8 '14 at 11:02

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