I'm trying the current gnus and mailcrypt. There is some breakage.
Test #1.
C-x m. I'm in Message mode. Make a simple test message. From
Mailcrypt menu, choose Sign Message. Send it.
When I receive the message under gnus, the signature is not
displayed. I have no way to know it's there! However, choosing
verify sigature succeeds.
Test #2. Just about the opposite result.
C-x m. I'm in Message mode. Choose Message/Attach File as Mime.
Attach a file. Again, Mailcrypt/Sign Message. Send.
Now view under gnus. This time, the signature is visible. Good.
Now try verify signature. It fails!