How do you select under emacs the key you sign/encrypt with when using mml?

Question

Long time mutt user, I am currently trying to learn how to deal with my mail from within emacs with the help of mu4e.

When it comes to signing mail, I use the following

(add-hook 'message-send-hook 'mml-secure-message-sign-pgpmime)

which automatically gets the job done.

As I have to manage several different keys / accounts, I am looking for the way to select the key I'll use for signing the message (epa-list-keys gives me three answers).

How do you select under emacs the key you sign/encrypt with when using mml ?

Answer 1

We can set

(setq mm-sign-option 'guided)

and now we will be prompted with key selection menu before sending a message.

As described:

mm-sign-option - Option of creating signed parts. nil, use default signing keys; guided, ask user to select signing keys from the menu.

We should be able to automate key selection based on e.g. From: field with help of

• Default Encryption

  DefaultEncrypt aims for automatic insertion of an MML secure encryption tags into messages if public keys (either GnuPG public keys or S/MIME certificates) for all recipients are available. In addition, before a message is sent, the user is asked whether plaintext should really be sent unencryptedly when public keys for all recipients are available.

• Keyfile field text auto-insertion

  ‘keyfile’ - File containing key and certificate for signer.

but I have never been annoyed enough to do so.

Answer 2

See: mml-secure-openpgp-sign-with-sender

If t, use message sender to find an OpenPGP key to sign with.

This set the key to match the From: for me. You can customize that variable too (and turn off the guided mode).