After getting ProxMox all setup, there was one last thing to investigate, mail was not flowing from the ProxMox host. Taking a quick look, two changes were required.
- The Postfix aliases database wasn’t initialized, so it was throwing an error, simply running “newaliases” on both nodes resolved this error.
- As port 25 is blocked by my host, all mail has to go through my ISP’s mail servers. Since I already have a Postfix server configured to handle this, setting the “relayhost” value in “/etc/postfix/main.cf” resolved this issues easily enough.