Proton Mail Bridge Thunderbird setup guide for Windows, macOS, and Linux

7 mins
Email app configuration

Proton Mail Bridge(new window) is an open-source application that allows you to fully integrate your Proton Mail account with any program that supports IMAP and SMTP. This includes Microsoft Outlook, Mozilla Thunderbird, and Apple Mail.

It runs in the background on your computer and seamlessly encrypts and decrypts your mail as it enters and leaves your computer.

Before you configure Thunderbird to use Proton Mail, you must first sign up for a Proton Mail account(new window) and download and install Proton Mail Bridge(new window) on your computer.

Once you’ve installed and added your account(s) to Proton Mail Bridge, you will need to configure your email client. Proton Mail Bridge works with most email clients and applications that support IMAP/SMTP connections.

In this guide, we provide step-by-step instructions for configuring Mozilla Thunderbird for use with Proton Mail Bridge in Windows, macOS, and Linux. Watch our video guide, or follow the step-by-step instructions below.

How to set up Mozilla Thunderbird for Proton Mail Bridge

1. In Windows and Linux, open Thunderbird, right-click in the sidebarSettings.

Open Settings in Windows and Linux
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In macOS, go to ToolsAccount Settings.

2. Click Account Actions and select Add Mail Account from the dropdown menu.

3. Enter your name, email address, and Proton Mail Bridge password from your Proton Mail Bridge account settings. 

Your Proton Mail Bridge account details
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The rest of the settings (security settings, ports, etc.) should be filled in automatically, but you can check this by clicking on the Manual Config button.

Enter your Proton Mail Bridge login details
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You also need to click Manual Config if you are using a custom domain. Enter all the settings provided in Proton Mail Bridge by clicking on Mailbox configuration under your account username. Do not use your regular Proton Mail account details

Enter the other settings shown in Proton Mail Bridge
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4. You will be asked to confirm a security exception for Port 1143 on server hostname This is your localhost port, which means that the certificate we provide must be self-signed, and is therefore not trusted by default in Thunderbird.

 Confirm Security Exception
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5. Thunderbird will now fetch your emails, which can take up to five minutes. You can send emails immediately.

You can send emails while you wait
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You will need to configure some additional settings for Thunderbird to work correctly with your Proton Mail account. 

6. In Windows and Linux, go to your Inbox, right-click your account name → Settings. In macOS, go to the menu barToolsAccount Settings.

7. Go to Copies & Folders and disable Place a copy in. Then scroll down to Drafts and Templates and make sure that drafts are kept on Local Folders. (On some Thunderbird setups, Local Folders is instead called your default account name).

Fill in some advanced settings
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Note: Drafts are saved on your local device only. If you create a draft in Thunderbird on your laptop, it will only be saved and accessible on that device.

You can now use Thunderbird with Proton Mail Bridge.


1. Keeping Thunderbird’s built-in spam filters enabled in addition to using Proton Mail’s spam filters provides additional spam filtering that uses the body of your messages to help detect spam. Any spam senders detected in this way will be added to your Proton Mail blacklist.

However, if you wish to disable Thunderbird’s spam filters and rely solely on Proton Mail’s spam filters, go to Account Settings → Junk Settings and disable Enable adaptive junk email controls for this account.

Disable Thunderbird’s spam filters
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2. When you send your first message, you may see a Send Message Error

you may see a Send Message Error
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Press OK to Confirm Security Exception for port 1025 (used for the SMTP server).

Confirm Security Exception
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3. In split addresses mode every IMAP account that you set up with Proton Mail Bridge is address-specific and will only be able to send and receive emails from the address it is set up with.

You can add any number of addresses to Outlook, but wait for one address to download before adding another.

Split address mode
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4. In combined addresses mode, you will need to add your non-primary addresses to Thunderbird in order to send with them.

To add an address in macOS, go to Account SettingsAccount NameManage Identities.

In Windows and Linux, select your accountAccount SettingsManage identities → select your identityEdit.

Add your non-primary address to Thunderbird
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Enter the Name and Email Address of your additional address and click OK.

Enter your Name and Email Address
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