Off the top of my head I can think of one alternative if metadata confidentiality or anonymity matter:

Bitmessage: https://github.com/Bitmessage/PyBitmessage

Bitmessage hides non-content metadata and uses a flood mixnet to unlink sender and receiver from eavesdropper view.

There is no alternative for email. Email clients support PGP and that's it. PGP does guarantee authenticity of a message due to digital signatures. PGP does not hide metadata about sender and receiver.

If you want truly confidential communication you have to set up a private pipeline. If you are using a public paid or free email service, you have zero confidentiality. Even if your message is encrypted, the email operators know who you are talking to.

#PGP #Email #Encryption #Privacy