3 ms·

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

• rstupek 1y ago
  You are correct that is the expected order of operations
• vidarh 1y ago
  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.