The mailgw needs to *recursively* (depth-first) search for a 
text/plain part in incoming emails. A GPG-signed message with an 
attachment looks like: 
 
multipart/signed 
  multipart/mixed 
    text/plain 
    application/x-pdf 
  application/pgp-signature 
 
which is not handled at all :) 
 
 
It'd be so cool to have validation of the signature too, but that's 
for another day :)