ProtonMail Bridge 3.23.1

ProtonMail Bridge: Editor's review of secure desktop integration

ProtonMail Bridge by Proton Technologies AG brings ProtonMails end-to-end encryption to desktop email clients, letting you use Outlook, Apple Mail, Thunderbird and other IMAP/SMTP apps while preserving ProtonMails privacy model. Designed for paid Proton Mail plans, Bridge runs locally, creates a secure local server, and decrypts messages on your machine so you can keep your existing workflow without sacrificing security.

Key features

• Seamless IMAP/SMTP integration  Connects ProtonMail accounts to mainstream desktop clients by creating a local email server.
• End-to-end encryption  Encrypts messages and attachments so only intended recipients can read them.
• Local-only keys and passwords  Uses a Bridge-specific password that never leaves your device and does not permanently store decrypted message data on disk.
• Cross-platform support  Available for Windows, macOS, and Linux.
• Offline access  Download and read encrypted mail via your desktop client when away from the internet.

How ProtonMail Bridge works

Bridge runs as a background desktop application that transparently encrypts and decrypts messages as they enter and leave your computer. It exposes a local IMAP/SMTP endpoint that your email client connects to, routing all ProtonMail traffic through the Bridge so your client behaves like it would for any other email account while retaining ProtonMails protection.

Security and privacy

Security is the core selling point for ProtonMail Bridge. The app was built to keep sensitive material private while enabling desktop client features:

• Passwords never leave your machine  The Bridge-specific password is stored locally and not transmitted to Proton servers.
• No permanent decrypted storage  ProtonMails design avoids long-term persistent storage of PGP keys or plaintext messages on disk.
• Background encryption/decryption  Operates transparently so encrypted traffic is handled securely without manual intervention.

Compatibility and requirements

Bridge supports major desktop clients and operating systems but requires a Proton Mail paid plan that includes Bridge access. Check system requirements before installing.

• Supported clients  Microsoft Outlook, Apple Mail, Mozilla Thunderbird, and other IMAP/SMTP-capable apps.
• Supported OS  Windows, macOS, Linux (consult Protons support pages for specific versions).
• Account level  Available only with paid Proton Mail plans that include Bridge.

Setup, usability and workflow

Installing Bridge is straightforward: install the desktop app, sign in with your Proton Mail account, copy the local IMAP/SMTP configuration into your email client, and start sending and receiving encrypted mail from your familiar interface.

• Quick configuration  Generates local server credentials you paste into client account settings.
• Keep client features  Use rules, search, folders/labels, and offline storage provided by your desktop client.
• Transparent operation  Runs in the background so everyday email use is unchanged.

Performance, updates and support

Proton regularly updates Bridge to improve compatibility and security. Performance is generally dependent on your local client and system resources; Bridge is lightweight and optimized to run continuously without noticeable overhead. For technical questions or troubleshooting, Protons knowledge base and support pages provide detailed setup guides and security documentation.

Who should use ProtonMail Bridge

Bridge is ideal for users who need ProtonMails encryption but prefer desktop clients for advanced features, offline access, or organizational workflows.

• Professionals who rely on Outlook or Apple Mail features.
• Power users who store mail locally and need offline access.
• Organizations that require encryption without changing user workflows.