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!
Yes, Postfix can act as an MSA by enabling the
submission section of
master.cf and making changes to the
smtp_ configuration options as desired. This is disabled by default; the tutorial you are following should instruct you to enable it as part of the setup process.
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.