We have just implemented an Exchange 2007 server into an organisation, it is running in the same forest and will eventually be replacing one of the exchange 2003 server. All users residing on the Exchange 2007 server receive internal emails (from Exchange 2003 users) with no text and just a winmail.dat attachment. This happens with RTF or HTML, all mail clients are Outlook 2007 SP1. Plain text is received ok. Exchange 2007 to Exchange 2007 users have no problems. Only other issue is Free/Busy information is not being retrieved from any user.
Have checked everything I can, the messages are being routed through the routing group connector. Exchange 2003 users receive all internal messages with no problems. There is no problem with any mail received from outside the organisation. Just internal from 2003 users to 2007.
Have been going through this issue for the last day now, have done many migrations and never encountered this issue. Any assistance would be greatly appreciated.