AnnealMail is an experimental, unauthorized fork of Enigmail to use post-quantum computer encryption in place of GPG/PGP encryption.
In the first stage, you should be able to install AnnealMail as a Thunderbird plugin, and sign and receive e-mails using CodeCrypt
I may need to write ccr-agent to replace gpg-agent for key management.
Open source, Mozilla Public License 2.0 (same as Enigmail)