Allow me to suggest another not-sufficiently-uncommon problem:
Attempting to end the headers of a message with a line consisting of a
single blank. Ie, CR LF SPACE CR LF instead of CR LF CR LF.
The space keeps the headers from ending, and the poor recepient mailer
proceeds to try to digest the body of the mail as though it were more
This is a common BITNET problem, since BITNET is record oriented and zero
length records are illegal in punch format files. Therefore there is no choice
but to have one spaec on the line between the header and body.
Gateways should, of course, remove the blank. PMDF does, but I'm sure that
plenty of software doesn't.