Working out upgrade of old 1.x + 2.x Dovecot installs to latest 2.3.2.1 out of Ubuntu Bionic repositories. _______
https://wiki.dovecot.org/Services suggests Dovecot can be used for full mail infrastructure, avoiding the complexity of exim4 or other MTA setup/management. Let me know if I understand this correctly. 1) https://wiki.dovecot.org/Submission can be used to listen on port 25 + port 587 (with auth). 2) https://wiki.dovecot.org/Pigeonhole can be used for filtering, including forwarding email to other machines. 3) https://wiki.dovecot.org/Pigeonhole/ManageSieve/Configuration can be used to forward off machine email, for example flowing through a relay service like MailGun, using a simple script or service like ESMTPD. 4) https://wiki.dovecot.org/LMTP can be used to deposit messages into filesystem as Maildir or dbox or mdbox backing stores.
