Postbox lists a plugin for "Enigmail," described as "Send and receive signed and encrypted messages using OpenPGP provided by GnuPG." I (obviously!) don't use

Postbox lists a plugin for "Enigmail," described as "Send and receive signed and encrypted messages using OpenPGP provided by GnuPG." I (obviously!) don't use Enigmail, but I've been a happy Postbox user for years. It also works fairly easily with S/MIME, which is what I've used for signing and encryption in the past.