Proton Mail Bridge

Proton Mail Bridge is a tool that allows end users of Proton Mail to send and receive email using traditional protocols (i.e. SMTP and IMAP).

It can be installed and run on a desktop machine but there is an unofficial docker image which you can use to run it as a service for applications that need to send automated emails.

In order to use it I created a simple Docker Compose file:

version: "2.0"
services:
    bridge:
        image: shenxn/protonmail-bridge:latest
        restart: unless-stopped
        volumes:
            - /mnt/user/Docker/protonbridge/data:/root
        ports:
            - 1025:25
            - 1143:143

1. On first run I did docker-compose run -i bridge init which displays a terminal.
2. Enter login and use your proton login info
3. now enter info and you should be given some credentials for logging in to SMTP and IMAP locally. You can use these for web apps that need to send emails or devices on the same network as your docker host that need IMAP access. Remember to replace the IP address 127.0.0.1 with whatever your docker host's address is.

TLS Certificate Warnings

You will probably find that downstream applications complain about the TLS certificates on your bridge server being funny when you try to connect. Certificate verification is very useful and should not be turned off if in doubt. I am using both the bridge and the things connecting to the bridge are on my home LAN and I am reasonably confident that there is very limited risk of a man-in-the-middle attack from inside the network so I've turned off TLS verification. If you're connecting to a bridge over the open net I would strongly recommend doing this properly (get the certificates from the vault and add it to your application's trust store properly).