I’ve been hosting my own DNS for a while now. Going on.. hmmm… let’s see I started that job in 2011 and I had been hosting from home… probably 9 years. And I have a confession, I made a rookie mistake. My name servers didn’t match my registrar’s glue records. Essentially, a glue record is the NS records your registrar provides to find your name servers.
My bad… seems that some of my secondary domains have been missing email for awhile now.
Moral of the story, verify your DNS deployment.
Here are some tools to check: