https://itgovernanceportal.com/otrs/gpg-for-otrs/
OTRS has the possibility to sign and encrypt/decrypt e-mails via PGP/GnuPG/GPG and S/MIME. Learn how to configure OTRS to use GPG
how toencrypted communicationconfiguregpgpgp
https://easypractice.net/apps/encrypted-messages/
Jul 11, 2023 - With our encrypted messages app (GDPR compliant), you can easily communicate with your clients through encrypted messages. Try it now.
secure communicationencryptedmessagesclients