This problem has occurred last week when I was trying to send email as well as waiting email from another person. I have a domain (@k***s.com), and while I am able to send and receive to/from everybody else, one specific person is unable to receive mine, and send to me (he is also able to send and receive to anyone else. The exact error he receives as he forwarded it to me, is below:
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:
"*@k****s.com": domain has no mail exchangers
P.S: I use a server with MDaemon installed. It is clean from viruses etc.