The second password is a decryption password which is never sent to us. After that, encrypted data can be retrieved.

'The first password is used to verify the identity of the user. Additionally, ProtonMail utilises a segregated authentication and decryption system, which forces a ProtonMail private email account to require two passwords. The Geneva-based company says that ProtonMail offers end-to-end encryption, and insists that no unauthorised eyes will be able to read your conversations. The email client in question, ProtonMail, was until now available on an invite-only basis.

In the light of revelations made by the whistleblower Edward Snowden, in 2014, developers and privacy advocates united to make an email client that nobody could eavesdrop on. Developed by enthusiasts from MIT and CERN, the Switzerland-based free email client announced this week that its Android and iPhone apps are now out of beta and available to all. If you don't want governments - or any unauthorised person - to read your email, you will want to try out the ProtonMail encrypted email service.

Proton email apps