This seems to be an old issue but I just started getting it on my system. Currently running Exchange 5.5 SP3 on Windows 2000 SP4
Sometimes users get an email like this:
Sent: Tuesday, March 08, 2005 11:06 AM
The Microsoft Exchange Server received an Internet message that could not be processed. To view the original message content, open the attached message.
This only seems to happen when the message has an attachment , background or is in HTML format. I have already searched the MS Kb and found info on Exchange 5.0 and Article ID: 270614 which is no help. This Exchange server was running NT4 for three years and didn't have this problem. Now that I have upgraded to Windows 2000 this message pops up. It doesn't happen every time and sometimes the sender can send the message twice and it works correctly on the second try. I see that there is a SP 4 on Microsoft's site, should I try that first?