Anthony,
Check the serialno of the dns zone file and update
it. If you entered the MX, but the change is not
propagated, it's likely due to a forgotten serial number
update.
Then, if you use Microsoft DNS Server, try
to switch off WINS lookup within DNS. The MS proprietary DNS extensions
will disable zone transfers to the other slave servers (unknown record type
WINS). If you ask your own DNS Server, the answer will be correct, but if you
ask any other DNS, the answer will vary depending on which NS the request
is routed to.
Marius
