If you want encrypted instant messaging, I'd recommend the Matrix ecosystem, using the Element apps.[0] For an email-based protocol, I would suggest Delta Chat

If you want encrypted instant messaging, I'd recommend the Matrix ecosystem, using the Element apps.[0] For an email-based protocol, I would suggest Delta Chat[1], which is backwards compatible with existing email accounts, and follows the Autocrypt approach to PGP[2]. [0] https://element.io/ https://element.io/ [1] https://delta.chat/en/ https://delta.chat/en/ [2] https://autocrypt.org/ https://autocrypt.org/