> I am facing the same problem now, but may have a bit more information. Original message has a multipart/signed structure with a qp text and a signature part, all of which is wrapped into a multipart/mixed structure, presumably done by the list server for the purpose of adding a (text, 7-bit) footer. Exchange flattens the struture into a multipart/ mixed with a qp text part, a application/pgp-signature part in base64, and another base64 text part.
I presume mutt needs multipart/signed.
