a not really related fact. I remember reading some RFC, and the sender should try sending to the server specified in A record if there are no MX records present
a not really related fact. I remember reading some RFC, and the sender should try sending to the server specified in A record if there are no MX records present
This sounds like it's an inbound check, as part of spam prevention, by seeing if the sending domain looks legitimate. There are a whole lot of those that are common that are not covered in RFCs.
You are correct that is the expected order of operations