Problem with SMTPSEND.DNS.MxLoopback

Hi All,

Some of my users have troubles when they sending an emails:

Error:

#554 5.4.4 SMTPSEND.DNS.MxLoopback; DNS records for this domain are configured in a loop ##

I have internal zone in my dns server  for my External DNS Name, and all MX records configured correctly (pointing to internal IP of mail server).

I don't have EDGE Server, just a HUB. This problem is only when users sending email to another users inside of my organization ( even to mailboxes in One Database ).

Please help me to solve this problem.

Best Wishes, Andrew Golubenkoff