GNU Emacs comes with built-in support for
GnuPG, e.g., via the EasyPG
Assistant, which is
able to en- and decrypt files with the extension
.gpg transparently if
you put the following into your
(require 'epa-file) (setq epa-file-encrypt-to "<your keyid>")
Moreover, Gnus supports GnuPG via the insertion of so-called MML secure tags, which contain encryption instructions to be performed before a message is sent. However, in the past I sent plaintext e-mails (more than once, I’m afraid) that really should have been encrypted ones. To prevent myself from forgetting to encrypt e-mails again, I wrote DefaultEncrypt.
DefaultEncrypt aims for automatic insertion of MML secure tags into messages if public keys (either OpenPGP public keys or S/MIME certificates) for all recipients are available. In addition, before a message is sent, the user is asked if plaintext should really be sent unencryptedly when public keys for all recipients are available.
My signed versions are available here: