On Thu, Nov 26, 2009 at 12:38:01PM +0530, Aneesh Kumar K. V wrote:
> message-mode can sign the message using C-c RET C-s
> which is mml-secure-message-sign

Thanks so much, Aneesh!  That's great.  I was not aware of those
abilities in mml mode.  I just noticed that epa-mail-{sign,encrypt}
can do this as well, but much less cleanly.  So the mml commands are
exactly what I was looking for.  Well, at least exactly *half* of what
I was looking for...

So the issue now is verifying/decrypting signed/encrypted received
mail.  Playing around with it a bit more, I've found a couple of
interesting things.  If I'm viewing an encrypted message with
notmuch-show, and if I type 'v' (notmuch-show-view-all-mime-parts), I
get the full message view, and then a prompt to:

Decrypt (PGP) part? (y or n)

Typing 'y', I see that there is some communication with my gpg agent
(I get a gpg agent password prompt), but then once the password is
entered, nothing happens, ie. I don't see the decrypted part.  I'm
trying to figure out where the problem is here.  Presumably something
is failing to capture the output of the gpg decryption.  I'm not clear
either about what mode is trying to do this decryption.  Is this epa?

Unfortunately nothing at all happens when I hit 'v' when viewing a
message that has OpenPGP signature attachment.

I also just discovered that there are some
epa-mail-{sign,verify,{de,en}crypt} commands that work similar to (but
not as cleanly as) the mml commands.  Unfortunately none of this is
very coherent.  And some sort of integration with notmuch-show would
be sweet.

jamie.