What is Hushmail?

Hushmail is an encrypted proprietary web-based email service offering PGP-encrypted e-mail and vanity domain service. Hushmail uses Open PGP standards and the source is available for download. If public encryption keys are available to both recipient and sender , Hushmail can convey authenticated, encrypted messages in both directions. For recipients for whom no public key is available, Hushmail will allow a message to be encrypted by a password (with a password hint) and stored for pickup by the recipient, or the message can be sent in clear-text. In July, 2016, the company launched an iOS app that offers end-to-end encryption and full integration with the web mail settings.

For more:- https://en.wikipedia.org/wiki/Hushmail