Proton Mail has gained popularity as a secure email service, prioritizing privacy with end-to-end encryption. However, accessing Proton Mail through traditional email clients requires Proton Mail Bridge—a local IMAP/SMTP server that manages encryption and decryption. For Synology NAS users, integrating Proton Mail can enhance email accessibility within their home server ecosystem. While Proton does not provide an official Docker container for the Bridge, community-developed solutions allow its deployment on Synology NAS.

This article explains the setup process, covering both official methods and the most efficient community-supported Docker solutions to run Proton Mail Bridge on a Synology NAS.

What Is Proton Mail Bridge?

Proton Mail Bridge is an intermediary that connects Proton Mail accounts with traditional email clients that do not support end-to-end encryption. It runs in the background, encrypting outgoing and decrypting incoming emails. Available for paid Proton Mail users, the Bridge supports Windows, macOS, and Linux.

Over recent years, Proton Mail Bridge has seen major updates, including:

  • Faster Syncing: A February 2023 update improved sync speeds by up to 10 times.
  • Enhanced Email Handling: Sending large attachments is now 3 times faster.
  • New IMAP Library: The introduction of Gluon, which uses a snapshot system, ensures better syncing across multiple devices.

However, Proton Mail has yet to provide an official Docker container, leading to the development of unofficial but effective Docker-based solutions.

Setting Up Proton Mail Bridge on Synology NAS Using Docker

The most widely used community-developed container for Proton Mail Bridge is shenxn/protonmail-bridge-docker. This implementation supports various NAS models, including ARM-based devices.

Prerequisites

Before starting, ensure your Synology NAS meets the following requirements:

  • DSM 7 or later installed.
  • Docker package installed (available via the Package Center).
  • A paid Proton Mail subscription.
  • Basic knowledge of Docker and Synology DSM.

Step-by-Step Installation Guide

Step 1: Install Docker on Synology NAS

  1. Open Package Center on DSM.
  2. Search for Docker and install it.
  3. Once installed, open Docker to manage containers.

Step 2: Download and Configure the Proton Mail Bridge Container

Option 1: Using Docker UI
  1. Open Docker on DSM and go to the Registry tab.
  2. Search for shenxn/protonmail-bridge-docker and download it.
  3. Go to Image and launch the downloaded container.
  4. Configure volume mappings and network settings before running the container.
Option 2: Using Docker Compose (Recommended for Flexibility)
  1. Enable SSH in DSM via Control Panel > Terminal & SNMP.
  2. Access Synology NAS using an SSH client (ssh admin@NAS-IP).
  3. Create a directory for the Bridge:
    mkdir -p /volume1/docker/protonmail-bridge
    cd /volume1/docker/protonmail-bridge
  4. Create and edit a docker-compose.yml file:

    version: '3'
    services:
    protonmail-bridge:
    image: shenxn/protonmail-bridge-docker
    container_name: protonmail-bridge
    restart: unless-stopped
    volumes:
    - protonmail:/root
    ports:
    - 1025:25
    - 1143:143

  5. Save and run the container:
    docker compose up -d

Step 3: Initialize Proton Mail Bridge

After deploying the container, initialize the Bridge and add your Proton Mail account.

  1. Run the following command to start initialization:
    docker run --rm -it -v protonmail:/root shenxn/protonmail-bridge init
    Or, if using Docker Compose:
    docker compose run --rm protonmail-bridge init
  2. Enter your Proton Mail login credentials.
  3. Retrieve IMAP/SMTP credentials by running:
    info
  4. Exit the setup by typing:
    exit

Step 4: Start the Proton Mail Bridge Container

To ensure the Bridge runs continuously, start the container using:
docker run -d --name=protonmail-bridge -v protonmail:/root -p 1025:25 -p 1143:143 --restart=unless-stopped shenxn/protonmail-bridge
Or via Docker Compose:
docker compose up -d

Step 5: Configure Your Email Client

Use the following settings to connect your email client to Proton Mail Bridge:

  • IMAP Server: Your Synology NAS IP
  • IMAP Port: 1143
  • SMTP Server: Your Synology NAS IP
  • SMTP Port: 1025
  • Username & Password: Credentials from the info command

Alternative Method: Direct SMTP Configuration

Some users have reported success configuring Proton Mail’s SMTP directly on Synology NAS for sending emails without using Bridge. To set up:

  1. Open Control Panel > Notification > Email.
  2. Choose Custom SMTP Provider.
  3. Enter the following details:
    • SMTP Server: mail.protonmail.ch
    • SMTP Port: 25
    • Authentication: Unchecked
    • Secure Connection: Checked
    • Sender Email: Your Proton Mail address

Note: This method allows only outgoing emails and does not support receiving messages or managing the inbox.

Troubleshooting Common Issues

Connectivity Issues

  • Ensure your email client can access the NAS’s IP.
  • Check that Docker’s network mode allows external access.

Password Manager Errors

  • If Proton Mail Bridge reports missing password manager support, it’s safe to ignore. It automatically sets up storage in headless environments like NAS.

Container Stability Issues

  • If the Bridge becomes unstable:
    • Update the container (docker pull shenxn/protonmail-bridge-docker).
    • Try a different Docker implementation (wormi4ok/proton-bridge-docker).
    • Check DSM and Docker logs for errors.

Conclusion: The Best Proton Mail Bridge Setup for Synology NAS

As of 2025, unofficial Docker implementations remain the best way to integrate Proton Mail with a Synology NAS. The shenxn/protonmail-bridge-docker container provides broad support for different NAS models and maintains reliable IMAP/SMTP functionality.

While an official Docker container from Proton would be a welcome addition, community solutions effectively fill the gap. For users needing basic email notifications only, direct SMTP setup may be a simpler alternative.

With Proton Mail Bridge continuing to receive updates, future integration with NAS devices may become even smoother, making privacy-focused email solutions more accessible to all users.

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