Delivering locally through the Submission Server

[John Stoffel]

R> I am learning Dovecot step by step. I have enabled the Submission
R> Server, in the hope that I would not need to learn other MTAs like
R> Postfix.

It's not that hard to setup postfix to accept incoming email from the
internet and your local users, and to then pass it to dovecot as
needed.  Dovecot is for IMAP/POP (shudder) access of your stored
emails.  It's not for sending email, or even receiving it from the
outside world.  

R> The Submission Server is very comfortable: it picks up the existing
R> Dovecot configuration, so that you do not need to configure any
R> user authentication separately. It is working fine on my test
R> setup.

It's not hard to setup postfix/dovecot to use the same
authentication.  My system used plain files.  Trivial. 

R> My first thought was that, if the recipient is a local mailbox, the
R> Submission Server would not need to relay the message to any
R> external SMTP server, as it could just deliver it locally. After
R> all, it is running on the same Dovecot.

Really, you're trying to optimize the wrong thing.  Just setup a
linode (or anything else except digital ocean since charter.net blocks
them completely for email delivery) at $5/month and install
postfix/dovecot together.  Works great.

John