We have an application in house that generates PDF files for delivery, then uses Exchange 2007 HUB servers to relay to email recipients outside of our company. What we know is that this relay to internal email addresses works fine, to gmail works fine. We have one domain that get's a winmail.dat file instead of a PDF file. Is there a good way to troubleshoot this issue. Or, what could I look for at the recipient layer? Can I also do a message tracking log search for attachments? Why is this one domain getting winmail.dat files?d

In EMC, Go to Organization Config->Hub Transport->Remote Domains Add a new remote domain for the that is receiving winmail.dat. In the properties of that remote domain, on the Message Format tab in the Exchange rich-text format: section, select 'Never Use' and click OK. I had the same issue where the remote system did not understand RTF and they were receiving winmail.dat instead of what was expected.

I'll give this a shot, thanks. Does this add any overhead to the Exchange servers?d

The overhead is negligible. All this is doing is telling exchange when the domain matches, only use plain text for that domain.

Thanksd