Sometime a month or two ago, sending email to my family stopped working. My emails vanished into the void and were never heard from again.
I figured my SMTP was set up incorrectly so no big deal, I used another (gmail etc.). Recently I got around to looking in my logs and I discovered:
Jul 23 17:06:49 ffclassic postfix/smtp: 73B3C4654756: host mx2.comcast.net[220.127.116.11] refused to talk to me: 421 IMTA24.emeryville.ca.mail.comcast.net comcast Reverse DNS failure : Try again later
Well that's no fun. I guess Comcast doesn't like talking to mail servers without reverse DNS set up properly. So now I fixed it (hopefully, we'll see in 24 hours).
These are the joys of running my own server. I had the option from my host of getting CPanel or its equivalent, or setting up everything by hand, so I chose by hand. The bad thing is that I have no idea what I'm doing. The good thing is there's no better way to learn than writing all of your config files by hand.