Freron MailMate

Currently this happens in compose mode:

1) Exchange encrypted mail with recipient A. -> MailMate defaults to encrypted when A appears in the list of recipients (or is the first?)
2) Compose a mail to recipients A and B where B does not have a PGP key.
3) Hit send -> Popup: can't encrypt to B -> disable encryption for this mail.
4) Compose a new mail to A only -> Encryption is disabled and needs to be enabled by hand again.

I think the heuristic when to default to encrypted could be either more configurable or more opportunistic:

• If I have never sent an encrypted mail to B and no key is known for B, then the popup in 3) is not necessary. The composer should default to "not encrypted".
• In step 4, the default should be encrypted because all previous e-mail with A only has been encrypted, a key is known and this is just the right thing to do.

Maybe MailMate could look back a few mails and implement some (very easy) logic for multiple recipients: Default to encrypt if all recipients like encrypted mail (= have received encrypted mail in the last few mails).

I think the behavior of enigmail in Thunderbird is pretty smart and works similar to what I suggest above.