Currently the mailgw code treats multipart/alternative as a 
multipart/mixed. We need to be more strict about this:

1. when performing the initial search for our text/plain message, we 
must discard an HTML alternative to the message,
2. we should preferrably *not* discard "related" parts to the HTML 
alternative (ie. images, etc) but rather keep them as attachments

As for what to do with a multipart/alternative found during the 
*post* text/plain message search for attachments, well, I have no 
idea. Perhaps just grab the first alternative and discard others.