I'm having trouble with a server that I administer.
I've been told that a number of emails aren't coming through. These are consistently from certain people. Here's the bounce error that they receive:
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address failed:
"firstname.lastname@example.org": domain has no valid mail exchangers
I don't know how to approach this. Obviously I have mail exchangers as we can send and receive email (usually) without a problem.
Is there anything I can do on our end or do I need to should I contact the postmaster for the domain that can't find the mail exchanger?