How to resolve connection issues in Bridge

Proton Mail Bridge requires an active connection to the server to ensure timely and reliable mailbox updates. If the connection becomes unstable or disconnected, you may face temporary issues with your email client.

When the connection between Bridge and Proton servers is interrupted, IMAP and SMTP servers shut down to ensure email clients know the connection is no longer active.

In this article, we will cover typical causes of connection issues and provide solutions.

1. Issues caused by VPN software
2. Anti-virus and security software
3. Device and Firewall issues
4. ISP and Geoblocking issues

When Proton Mail Bridge is unable to reach Proton servers, a red notice will appear.

Your email client might also report an error.

Issues caused by VPN software

Modern VPN applications have a feature to block ads and/or malware. Proton VPN also includes this feature. You can learn how it works here(new window). 

First, make sure to disable Alternative Routing. This feature can sometimes conflict with a VPN. You can find this option in Bridge → Settings → Advanced Settings.

Alternatively, you can temporarily disable the VPN, then restart Proton Mail Bridge to see if the connection will be established.

Anti-virus and security software

Another cause for connection issues can be antivirus or other security software on the device. The process for allow-listing the Bridge will vary depending on your software.

For Windows, you should add an exception for the below path, assuming Bridge is installed in the default location.

C:\Program Files\Proton AG\Proton Mail Bridge\proton-bridge.exe

Some applications might require more allow-listing. Due to how Bridge seamlessly installs updates, there is also a proton-bridge.exe executable file in the below location, under the latest update version.

%AppData%\Roaming\protonmail\bridge-v3\updates

Make sure to allow-list both Program Files and the Updates folder to ensure they are not blocked.

Device or Network Firewall issues

Firewalls can also cause the Bridge to not work correctly, as it requires a connection to Proton servers. We recommend adding an exception for Bridge in your Firewall.

Device firewall

Here’s how you can allow an application to bypass your firewall.

1. Open the Start menu, type Allow an app through Windows firewall, and select it from the list of results.
2. Click Change settings. You might be asked for an administrator password or to confirm your choice.
3. To add an app, select the checkbox next to the app, or select Allow another app and enter the path for the app.
4. To remove an app, clear the checkbox next to the app, and then select OK.

Here is the path to the application: C:\Program Files\Proton AG\Proton Mail Bridge\proton-bridge.exe

If bridge.exe already appears here, make sure the network type you’ve allowed it for matches the network you are connected to.

Network firewall

On home networks, there is typically no network firewall with strict rules. However, if you’re on a corporate network, there might be a network firewall with more restrictive rules that are affecting the Bridge.

In this case, you will have to communicate with your IT administrators to see if they can help in allow-listing Bridge on the network.

Here are the Proton server addresses you should allow-list:

• mail-api.proton.me, ports 443 and 80
• IP Range: 185.70.40.0/22

ISP and Geoblocking issues

Unfortunately, ISPs or even countries can block the connection to Proton servers. In such cases you will not be able to connect from your device with that specific internet connection.

If you are not using a VPN, you can enable Alternative Routing from Bridge as that can help avoid censorship. This option is located in Bridge → Settings → Advanced Settings.

If that does not help, you can download Proton VPN(new window) — which is available to all users — and use it to connect to a server before opening Bridge.

 In rare cases, there might not be a way to resolve this issue apart from connecting to a different network. In extreme cases, such as what happened in Russia, connecting to another network will not work.