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Proton Mail Bridge

Copyright (c) 2024 Proton AG

This repository holds the Proton Mail Bridge application. For a detailed build information see BUILDS. The license can be found in LICENSE file, for more licensing information see COPYING_NOTES. For contribution policy see CONTRIBUTING.

Description Bridge

Proton Mail Bridge for e-mail clients.

When launched, Bridge will initialize local IMAP/SMTP servers and render its GUI.

To configure an e-mail client, first log in using your Proton Mail credentials. Open your e-mail client and add a new account using the settings which are located in the Bridge GUI. The client will only be able to sync with your Proton Mail account when the Bridge is running, thus the option to start Bridge on startup is enabled by default.

When the main window is closed, Bridge will continue to run in the background.

More details on the public website.

Launcher

The launcher is a binary used to run the Proton Mail Bridge.

The Official distribution of the Proton Mail Bridge application contains both a launcher and the app itself. The launcher is installed in a protected area of the system (i.e. an area accessible only with admin privileges) and is used to run the app. The launcher ensures that nobody tampered with the app's files by verifying their signature using a hardcoded public key. App files are placed in regular userspace and are signed by Proton's private key. This feature enables the app to securely update itself automatically without asking the user for a password.

Keychain

You need to have a keychain in order to run Proton Mail Bridge. On Mac or Windows, Bridge uses native credential managers. On Linux, use secret-service freedesktop.org API (e.g. Gnome keyring) or pass. We are working on allowing other secret services (e.g. KeepassXC), but for now only gnome-keyring is usable without major problems.

Environment Variables

Dev build or run

Integration testing

Folders

There are now three types of system folders which Bridge recognises:

WindowsMacLinuxLinux (XDG)
config%APPDATA%\protonmail\bridge-v3~/Library/Application Support/protonmail/bridge-v3~/.config/protonmail/bridge-v3$XDG_CONFIG_HOME/protonmail/bridge-v3
cache%LOCALAPPDATA%\protonmail\bridge-v3~/Library/Caches/protonmail/bridge-v3~/.cache/protonmail/bridge-v3$XDG_CACHE_HOME/protonmail/bridge-v3
data%APPDATA%\protonmail\bridge-v3~/Library/Application Support/protonmail/bridge-v3~/.local/share/protonmail/bridge-v3$XDG_DATA_HOME/protonmail/bridge-v3
temp%LOCALAPPDATA%\Temp$TMPDIR if non-empty, else /tmp$TMPDIR if non-empty, else /tmp$TMPDIR if non-empty, else /tmp

Files

Base DirPath
bridge lock filecachebridge.lock
bridge-gui lock filecachebridge-gui.lock
vaultconfigvault.enc
gRPC server jsonconfiggrpcServerConfig.json
gRPC client jsonconfiggrpcClientConfig_<id>.json
gRPC Focus server jsonconfiggrpcFocusServerConfig.json
Logsdatalogs
gluon DBdatagluon/backend/db
gluon messagesdatagluon/backend/store
Update filesdataupdates
sentry cachedatasentry_cache
Mac/Linux File Sockettempbridge{4_DIGITS}