I regularly get bogus bounces from clueless virus scanners that don’t realize the sending address is fake 99% of the time, but this takes the cake:

Sometime last night I received three copies of the same notice from some system in Brazil. They had written their virus warning in Microsoft Word, saved it as HTML without cleaning up all the extra junk, and made it the only part of the message… in Base64 encoding!

If you’re going to send any kind of diagnostic notice by email, you want it to be as simple and widely readable as possible. That means plain text (not HTML or Base64, and certainly not both!) It also means if you do want to use HTML, at least clean it up and include a plain-text alternative. For all you know it’s going to be read by some admin logging into a GUIless server through SSH over a modem connection on a hotel phone line!