I've documented an unfortunate MTA habit over in https://tools.ietf.org/html/draft-dkg-openpgp-pgpmime-message-mangling-00#section-4.1 which i've named "Mixed Up" mangling. In particular, popular versions of Microsoft Exchange take a multipart/encrypted e-mail and transform it unaccountably to multipart/mixed.
While the right thing to do long term is to get a fix for those MTAs (which i'm also working on, elsewhere), even if we succeed in doing that, messages that have already been mangled by them will live on in our mailboxes forever. What follows is a series of patches that lets a notmuch user deal with any message mangled in this particular form in a sensible way. In particular, they should be able to decrypt the message correctly despite its nonstandard structure. This represents a deviation from standard MIME handling procedures, but i believe it is a safe deviation, and a useful one. The test case included in this series should be sufficient to show the problem specifically, but if anyone wants to receive encrypted e-mail from me that demonstrates the problem to their personal key, i can provide. Please let me know by replying off-list and making sure i know your OpenPGP key fingerprint. If anyone has examples of other common, detectable, and repairable message manglings, please let me know. I'd be happy to add them to my documentation of this sort of thing at least, and if we can fix them up for notmuch users, even better. All the best, --dkg _______________________________________________ notmuch mailing list email@example.com https://notmuchmail.org/mailman/listinfo/notmuch