Why does somone trying to send me email get a “Domain of sender address does not exist” error?
That usually means that the sender’s domain (the part after the “@” symbol) isn’t capable of receiving email. This error message usually will only occur if the nameservers for this domain are reachable and answering queries but clearly announce that the domain doesn’t have any MX records and doesn’t resolve to an IP address (NXDOMAIN). This makes any bounce or reply messages impossible, and the sender’s email address is considered invalid. If the DNS servers are having temporary problems, and aren’t answering for the domain, the message would still be accepted. It’s only when the DNS servers for the domain authoritatively state that the domain can’t receive email that you will get this message. The sender should be specifying a valid email address when sending you an email. There are some times when this isn’t wanted, like if the sender doesn’t expect a reply, but it is quite normal for recipient mail servers to reject messages for this reason. What is the difference between an unwante
