Secure Mail ----------- Send notification mails to user encrypted with GPG. Each user can enable it and submit his public key under Settings-> Addon -> "Secure Mail" Settings. Use 'openpgp-php' library, a pure PHP implementation of GPG/PGP. See [project repo](https://github.com/singpolyma/openpgp-php). Need Friendica version > 3.3.2 to work.