Gpg-remailer is somewhat similar to ordinary mailing list software, but all e-mail processed by gpg-remailer is PGP/GPG signed and encrypted. Gpg-remailer's repository has moved to https://gitlab.com/fbb-git/gpg-remailer and is not maintained at this location anymore. The project's web-page can be found at http://fbb-git.gitlab.io/gpg-remailer
fbb-git/gpg-remailer
Gpg-remailer decrypts and verifies received mail and then sends it reencrypted to members of a well-defined group
C++