Postfix as MSA

[abrodski]

Hello!

I'm just curious whether Postfix also plays a role of MSA in a process of SENDING an e-mail? In other words, does MUA "talk" directly to MTA (say, Roundcube transfers an e-mail to Postfix without any help from MDA such a Dovecot)? Again, I'm asking about sending and NOT receiving!

[lammert]

Yes, postfix can be used for email submission through port 587 by clients. You have to enable this functionality though by un-commenting the submission line in the master.cf file. Also be sure to add an exception for port 587 traffic in your firewall to the server, because default firewall rules often block incoming access to port 587.

[abrodski]

I haven't touched it. So what happens in a default situation? Does Dovecot act as MSA? If not... Then I don't have MSA.
So which service submits the mail to Postfix then when it's about to be sent? MUA does it directly vs. Postfix? Is that so?

[lammert]

It depends on your configuration. If Dovecot is active and you use IMAP as a protocol, then Dovecot is the process accepting email submissions from clients. But it is also possible to use SMTP port 25 with authentication to accept email submissions.

[abrodski]

Dovecot is active. Frankly, I don't know whether it's IMAP or POP3 since I'm using webmail (Roundcube).

[lammert]

Roundcube uses IMAP

[abrodski]

So basically is my case Dovecot acts in both ways, either accepting messages from MUA when I'm sending or transferring them from MTA to MUA when I'm receiving?