Looks like RIM might have intentionally changed this in Service Pack 3. From the SP3 release notes:
BlackBerry Messaging Agent |
SDR 60681: Previously, if a user sent a message in HTML format from the GroupWise Client, the BlackBerry device received the message with a txt file attachment that contained the body of the message.
Seems like a poor decision on RIM's part to me. I understand stripping the attachment on a multipart text/plain and text/html message, but if the message is only text/html, the attachment at least enabled you to read the message.