I have a similar problem, we use NT4 with Exchange 5.5. If I send a safe attachment from OExpress(all versions) to OExpress, no attachment. I can send from outside our domain via Hotmail, etc and the attachment is there. I can send an attachment outside our domain and the message is there. OExpress to Outlook works fine also. Outlook to Outlook works fine. It started around 8/22, best guess. Any help would be greatly appretiated.
Regards,
Joe