I’m thinking of replacing the mailjet server that I’m currently using with my own postfix SMTP server. I am wondering, does Discourse need any incoming mail service such as IMAP or POP3?
You do need incoming email to allow people to participate by email, but you can use direct delivery instead of setting up a pop/imap account somewhere:
So do I do this with my Postfix or is this an alternative?
You can read that topic and learn all about it.