Apparently I installed that thing in 2006 and I last updated it in 2016, then I quit updating it for some reason that I totally forgot. Probably laziness…
It’s been running for quite some time and we kind of forgot about it in the closet, until the SSH tunnel we use to get our mail outside our home stopped working because modern openssh clients refuse to use the antiquated key cipher I setup client machines with way back when any longer.
I just generated new keys with a more modern cipher that it understands (ecdsa-sha2-nistp256) and left it running. Because why not 🙂
You need SPF, DKIM, DMARC with a RUA set up to an email that doesn’t bounce. That’s pretty much it. I’ve been running email servers a long time and actually set up email from a new domain/IP a couple of years ago as well.