Proton Mail Bridge is a background desktop app that adds a Proton Mail account to Outlook, Thunderbird, or Apple Mail through a local IMAP and SMTP server, keeping messages end-to-end encrypted.
Proton Mail Bridge solves a specific problem: the encrypted inbox lives in Proton's apps, while many people work inside a desktop email client. The Bridge runs quietly in the background, starts a local mail server on the computer, and presents the Proton account to that client over IMAP and SMTP. Messages are decrypted on arrival and encrypted on the way out, so the client behaves normally while the storage on Proton's side stays protected. Setup in Proton Mail Bridge means generating a Bridge password, adding the account to the client, and letting it sync. Once running, the mailbox looks like any other account, complete with the client's own search, rules, and signatures.
Who gets the most out of it? Anyone whose day runs through a mail client rather than a browser tab: legal and finance teams with filing rules, support staff who triage from a shared folder, and people who prefer a desktop client's keyboard shortcuts and offline search. Consistency is the quiet benefit. An invitation that arrived from Cisco Webex Meetings, a contract thread, and a newsletter all sit in the same familiar window, and the rules and folders that already organise that window keep working. Messages downloaded while the connection is good remain readable later, which is the difference between an archive you own locally and a mailbox you can only open online.
The first benefit of Proton Mail Bridge is continuity. Switching to encrypted email usually means abandoning years of habits, filters, and client-side tooling; the Bridge removes that trade-off by letting the existing client keep doing the work. The second benefit of Proton Mail Bridge is local control. Messages are stored on the machine as well as in the account, so they can be read offline, backed up with whatever tool the team already uses, and searched without waiting for a network round trip. Third, the security story is honest rather than absolute. The Bridge uses a password of its own, separate from the Proton login, and that password stays on the computer. Passwords never leave the machine, and PGP keys or decrypted message data are not permanently written to disk, which matters when a laptop is lost or inspected. Finally, it removes app fatigue: one inbox, one set of rules, one place to search, without moving the encryption boundary.
Key capabilities and highlights.
The Bridge creates a mail server on the computer itself, so a client connects to a local address rather than to Proton's servers directly, which is how standard clients can talk to an encrypted account without any plugin. No client modifications are required.
Proton Mail Bridge stays resident while it runs, decrypting messages as they arrive and encrypting them as they leave, so the mailbox reads normally in a client while the copy stored on Proton's servers remains encrypted end to end. It starts with the system.
Outlook, Apple Mail, and Mozilla Thunderbird are the documented companions, and any client that speaks IMAP and SMTP can use the same connection, which means the setup does not lock anyone into one particular program. Step-by-step guides cover the common combinations.
Messages can be pulled down while the connection is good and read later without one, so an archive stays usable on a flight or during an outage, and local search keeps working against the downloaded copy. That copy is also what makes external backups possible.
Each account connected through the Bridge gets a password of its own, distinct from the Proton login, and that credential is generated locally and never sent anywhere, so a compromised client password does not expose the main account password.
Proton Mail Bridge does not permanently store PGP keys or decrypted message data on the machine, which limits what a stolen laptop or a forensic inspection of the drive can reveal beyond the mail client's own local cache of downloaded mail.
Rules, folders, signatures, keyboard shortcuts, and plugins in the desktop program continue to work, so years of accumulated setup is not thrown away when a Proton account replaces an older mailbox. That continuity is usually the deciding factor.
Because the mail is also on the machine, the desktop client's own search and filtering run at full speed across the whole archive, which is often faster and more flexible than searching through a web interface for the same messages.
Browse historical releases and previous builds.
Common questions about Proton Mail Bridge.
It is a desktop application that connects a Proton Mail account to a standard email client by running a local mail server on your computer and handling encryption and decryption in the background.
Microsoft Outlook, Apple Mail, and Mozilla Thunderbird are the documented options, and any other client that supports IMAP and SMTP can be configured with the same connection details.
Yes. The Bridge is available only with a paid plan that includes Proton Mail, so the account has to support it before a desktop client can be connected this way.
Proton states that passwords never leave your machine, that PGP keys and decrypted message data are not permanently stored on disk, and that the Bridge password is separate from your Proton login password.
Yes. Messages downloaded through your client are stored locally, so they can be read and searched without a connection, and that local store can be backed up like any other mail folder.
Yes. It is a background app, and the client reaches your mailbox through it, so it is normally set to start with the system rather than opened only when you need to send something.
In two places. The account copy stays on Proton's servers under encryption, and the client keeps a local copy it can read offline, which is why local storage use is worth watching.
Windows, macOS, and Linux are all supported, with dedicated setup guidance for Linux, and the operating system you choose does not change how the account behaves inside the email client.
Proton Mail Bridge is a background desktop app that adds a Proton Mail account to Outlook, Thunderbird, or Apple Mail through a local IMAP and SMTP server, keeping messages end-to-end encrypted.
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