I was trying to debug a problem with sending mail to my customized
roundup instance, and all I was getting for error information was the
line "There was a problem with the message you sent:", followed by the
str of an exception, in the bounce message from the gateway.  There was
no error indication in the instance log.  This was not enough
information to track down the problem.  I added the logging line in the
attached patch to mailgw.py to log the traceback, and that led me
directly to the problem.