ProtonMail Bridge for e-mail clients.

After the container has started you will need to access the CLI to do the initial setup.
From Unraid terminal and run the following:

docker exec -it protonmail-bridge /bin/bash
chmod +x entrypoint.sh
./entrypoint.sh init

Wait for the bridge to startup, use login command and follow the instructions to add your account into the bridge. Then use info to see the configuration information (username and password). After that, use exit to exit the bridge.

You may need CTRL+C to exit the docker entirely.
Then restart the container.