sendmail and DNS on the same machine

I am struggling with sendmail in my environment where
the DNS and the sendmail servers are on the same box.
It keeps telling me "mail loops back to me (MX
problem?). I have spent over three days on this
problem and tried everything. The query using
nslookup from a client machine shows good information,
but I just can not send any mail to my domain email
addresses.

Thanks,
Naren

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