ProtonMail Introduces IMAP/SMTP Bridge
Basically, the downloadable Bridge app enables ProtonMail users to access their encrypted email accounts using their favorite email client, without compromising on the security provided by the end-to-end encrypted service, and without needing to modify their email application. At the same time, local copies of the emails are stored on the user’s computer, allowing them to use the search features of their email client as normal.
To achieve this, the Bridge app functions like a local IMAP/SMTP email server capable of communicating with the remote ProtonMail server to encrypt and decrypt incoming/outgoing messages locally. In this way, it translates end-to-end encrypted email data into a language that any email client can understand, thus “bridging” the gap between ProtonMail’s end-to-end encryption and a user’s standard email client.