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Why am I able to receive emails from some domains and not others?


In July 2009, our mail systems were updated to conform to RFC 2181 published by the Internet Engineering Task Force (IETF). Information about this change can be found at the IETF site below:

RFC 2181 - MX and NS records

"The domain name used as the value of a NS resource record, or part of the value of a MX resource record must not be an alias. Not only is the specification clear on this point, but using an alias in either of these positions neither works as well as might be hoped, nor well fulfills the ambition that may have led to this approach. This domain name must have as its value one or more address records. Currently those will be A records, however in the future other record types giving addressing information may be acceptable. It can also have other RRs, but never a CNAME RR."

As a summary, MX or Mail Exchange records for a given domain should not resolve through a CNAME but rather an A record or address record (IP address). Since the change in our mail systems in July 2009 to conform with RFC 2181, no email will be accepted by a domain with an MX record that resolves to a CNAME or alias.


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