Could you provide a patched version of mutt that includes encrypted and compressed folder support? It patches just fine against the sources found in a recent rsync in portage. See url for patch info.
I do believe that Calum was working on incorporating an entire set of cool patches for mutt.
I've added the compressed folder patch (and bumped revision to -r3). I plan on adding further patches. As we never gained any consensus as to the usefulness of the patches i suggested (in fact i recieved no responces from -core in this regard) I held off adding them.