What is Proton Mail Bridge used for?

Proton Mail Bridge is a desktop app that exposes local IMAP and SMTP servers so ordinary email clients can use a Proton Mail account. It is a good fit for using Thunderbird or Outlook with Proton Mail and syncing Proton Mail to a desktop mail client.

Is Proton Mail Bridge open source?

Yes. Proton Mail Bridge is open source under the GPL-3.0 licence. Its source code is on GitHub at ProtonMail/proton-bridge and is written mainly in Go.

Is Proton Mail Bridge free?

Yes. Proton Mail Bridge is open source, so the software itself is free to use.

Can I self-host Proton Mail Bridge?

Yes. Proton Mail Bridge can be self-hosted on your own server or infrastructure.

What are some alternatives to Proton Mail Bridge?

Similar open-source tools in the Email Clients & Servers category include FairEmail, Maddy and Mox. SaaS products in the same category include bytemailapp.com, Mailbird and Apple Mail.

Is Proton Mail Bridge actively maintained?

Yes. The most recent commit to Proton Mail Bridge was on 29 September 2026, and the latest release is v3.27.0, published on 9 September 2026. The project has 1.6k stars on GitHub.

Proton Mail Bridge: open-source email clients & servers

About Proton Mail Bridge

Proton Mail Bridge is a desktop application from Proton AG that lets standard email clients work with a Proton Mail account. When launched, it starts local IMAP and SMTP servers and shows a graphical interface. You sign in with your Proton Mail credentials, then add a new account in your email client using the connection settings that Bridge displays.

The email client can sync with the Proton Mail account only while Bridge is running, so the option to start Bridge on startup is enabled by default, and Bridge keeps running in the background after you close its main window. The official distribution includes a launcher installed in a protected system area that verifies signatures of the app files before running them, which allows secure automatic updates without asking for a password.

Bridge needs a keychain to run: native credential managers on macOS and Windows, and the freedesktop.org secret-service API or pass on Linux. The code is written in Go and licensed under GPL-3.0. The repository includes build information, contribution policy and licensing notes, and more detail is on the public Proton website.

Key features

Local IMAP and SMTP servers
Works with standard email clients
Runs in the background after closing the window
Signed launcher for secure automatic updates
Uses native or Linux keychain storage

Good fit for

→Using Thunderbird or Outlook with Proton Mail
→Syncing Proton Mail to a desktop mail client

Built with: Go
Tags: proton-mail; email; imap; smtp; desktop; privacy; go; email-client

Proton Mail Bridge: questions and answers

What is Proton Mail Bridge used for?: Proton Mail Bridge is a desktop app that exposes local IMAP and SMTP servers so ordinary email clients can use a Proton Mail account. It is a good fit for using Thunderbird or Outlook with Proton Mail and syncing Proton Mail to a desktop mail client.
Is Proton Mail Bridge open source?: Yes. Proton Mail Bridge is open source under the GPL-3.0 licence. Its source code is on GitHub at ProtonMail/proton-bridge and is written mainly in Go.
Is Proton Mail Bridge free?: Yes. Proton Mail Bridge is open source, so the software itself is free to use.
Can I self-host Proton Mail Bridge?: Yes. Proton Mail Bridge can be self-hosted on your own server or infrastructure.
What are some alternatives to Proton Mail Bridge?: Similar open-source tools in the Email Clients & Servers category include FairEmail, Maddy and Mox. SaaS products in the same category include bytemailapp.com, Mailbird and Apple Mail.
Is Proton Mail Bridge actively maintained?: Yes. The most recent commit to Proton Mail Bridge was on 29 September 2026, and the latest release is v3.27.0, published on 9 September 2026. The project has 1.6k stars on GitHub.