Have you seen consistent behavior when sending to these specific domains?
Are you seening NDR's occur always to these specific domains or is it
sporadic? Have you tried turning on Message Archival on your IMS to see if
all messages are dropping the domain part of the SMTP address? To do this
take a look at the following article.
258557 XFOR: How to Record Internet-Bound Messages Sent by a Specified
I wouldn't run archival for a long time as it causes a fairly hefty
performance hit and will fill up your drive if you deliver a lot of SMTP
mail, but you should get a better indication of what messages fail and
perhaps why. Please let us know what you find.
Richard C. Gates, MCSE, MCSA, A+
Online Support Professional
Microsoft IT Communities
This posting is provided "AS IS" with no warranties, and confers no rights.