Hi Jamie, notmuch developers,
On Tue, 03 Jan 2012 13:45:14 -0800, Jameson Graef Rollins <jrollins@finestructure.net> wrote:
> On Tue, 3 Jan 2012 20:56:51 +0100, Gregor Zattler <telegraph@gmx.net> wrote:
> > I replied to a PGP/MIME signed and encrypted e-mail and was
> > astonished to realise that my reply was sent unencrypted (and
> > unsigened for that matter).
> 
> Yikes!  Sorry this happened, and I hope nothing too sensitive was
> exposed.

No :-)

> Auto signing of outgoing mail can be enabled by the following [0]:
> 
> (add-hook 'message-setup-hook mml-secure-message-sign-pgpmime)
> 
> You can configure the message-setup-hook with the customization UI as
> well.

I tried this and enabled mml-secure-message-encrypt-pgpmime too.
I did a test with an address I have no public key for.  I was
informed of the fact and asked if I want to skip this key.  The
result was an email encrypted only to me (I suppose it's a
sensible default to include the key of the sender in the list of
key to encrypt to), so it would be unreadable for the recipient :-(

> Unfortunately, auto encrypting of replies to encrypted emails is not yet
> implemented.  It is desperately needed, though, obviously.  So this is a
> good excuse to start a discussion about how we could achieve this.
> 
> It just occurs to me that a way to do this would be to have notmuch
> reply add the appropriate mml #secure tag for encryption to the output
> reply template, maybe with something like a --emacs option.  That would
> be pretty easy to implement, although it would obviously be very UI
> specific.
> 
> Another possibility would be for notmuch reply to add some sort of
> header to the reply message to indicate that the original was encrypted,
> and then do something in emacs to try to read that header and add the
> appropriate mml #secure tag.  That would also be easy to implement in
> the notmuch CLI, and it would be more UI agnostic, but it would require
> a lot more elisp.
> 
> Or maybe we could support both?
> 
> Any other suggestions?

I'm no developer; your second suggestion sounds more plausible
me since notmuch is a frontend-agnostic mail system.

> > Actually the message buffer in which I write replies has Auto
> > Encryption Mode enabled, but nothing happens.  
> 
> That's unfortunate.  Can you explain exactly how you set this up, and
> how it didn't work?

Actually I did not set it up.  I tested this again with emacs23
-q ...  It has something to do with EasyPG and therefore I assume
it only works on the level of file encryption if the file
associated with the buffer ends in .pgp  But that's a guess.


[...]
> It's actually usually mml that is used with message-mode to
> sign/encrypt message, not epg.

Thanks for your info.  Actually I'm a mutt user and I customised
mutt to opportunistically encrypt emails if I/gpg have/has public
keys for all recipients of an email.  I have no clue how to
achieve this with Emacs.

Ciao; Gregor