I've been working for 3 days trying to find info about a SMTP error:

#5.5.0 smtp;552 MS-Office file containing VBA macros found inside of the email

Since I administer an Exchange server, I begin to immediately suspect that a recent Microsoft patch (MS06-019) was the problem. I do what any smart person does, immediately start googling to see who else had this message and what they did to fix it. Unfortunately nobody has, even in the newsgroups. Finally I give up after trying everything I can (changing/removing smarthosts, verifying no anti-virus on the server issue, etc.), and called Microsoft. After 3 and a half hours of them doing the same thing I had done, we found that our Sonicwall firewall had an anti-virus scanner that removes all email attachments that have VBA macros embedded. Another administrator had decided to turn on this feature without telling anybody else, and then did not even think about the error being due to his change (duh!). So... for those of you googling the same NDR message as me, check your firewall, it might fix your problem in 10 minutes instead of hours of research.