This is just a reminder to those people who run their own mail servers … make sure your backup MX’s are running properly.
I have a friend who’s company runs their own mail server … but they also have a backup MX listed. The main mail server accepted mail for my friend without a problem … but the backup MX didn’t know who he was.
I have a suspicion that the mail administrator for my friends company didn’t even know he had a backup MX setup.
Of course, if you don’t get a huge amount of email, consider saying NO to backup MX’s.
And, if you don’t know what a MX is at all … ignore this post. 🙂