Thanks. Where is that documented?
Problem - trying to run normal enterprise class Postfix server for mail on same server as Discourse container. I need to have email for other websites, but mail-reciever sits on SMTP port 25.
For lack of other guidance I thought I could attempt to change the mail-receiver SMTP port and use LMTP or something from Postfix to route messages for that domain to that port. But I am rather lost.