SMTPBroker

A simple local SMTP server that transform server alert email to Discord / Telegram message with attachment support.

There is a web UI to let you view the full message which is larger than the destination maximum length limit or HTML message.

Installation

The following shows the simplest setup, without any authentication. For security reason, please do not expose your SMTP (port 25) to the Internet.

First, create forwarder.yml.

- name: Discord
  forwarder: discord
  parameters:
    webhook: YOUR_WEB_HOOK_URL
#    content: "@everyone" # uncomment this if you want mention

#- name: Telegram
#  forwarder: telegram
#  parameters:
#    bot_token: YOUR_BOT_TOKEN
#    chat_id: YOUR_CHAT_ID

Then, create docker container.

docker run -d \
  --name=smtpbroker \
  --restart=unless-stopped \
  -e Web__Url=https://your-ip:8443 \
  -v $PWD/forwarder.yml:/forwarder.yml:ro \
  -v $PWD/data:/data \
  -p 8443:443 \
  -p 127.0.0.1:25:25 \
  brian9206/smtpbroker:latest

Authentication

You can set up SMTP or Web UI authentication by setting the environment variables

Add the following parameters to docker run command to enable authentication.

-e Web__Auth=true \
-e Web__User=YOUR_WEBUI_USERNAME \
-e Web__Password=YOUR_WEBUI_PASSWORD \
-e SMTP__Auth=true \
-e SMTP__User=YOUR_SMTP_USERNAME \
-e SMTP__Password=YOUR_SMTP_PASSWORD \

Multiple forwarder

You can set up multiple forwarders and let them to handle different "From" or "To" addresses.

- name: Synology Notification
  forwarder: discord
  rules:
    from: "synology@example.com"
    stop: true
  parameters:
    webhook: DISCORD_WEB_HOOK
    content: "@everyone"

- name: Telegram
  forwarder: telegram
  parameters:
    bot_token: BOT_TOKEN
    chat_id: CHAT_ID

The above example will make all email from synology@example.com notified in Discord, others to Telegram.

Note: you can use wildcard like *@example.com and to: rule also works.

HTTPS Certificate

By default, the server will automatically generate a self-signed certificate on startup. If you want to install your own certificate, use the following docker parameter:

-v $PWD/server.pfx:/ssl/server.pfx:ro \
-e ASPNETCORE_Kestrel__Certificates__Default__Password=YOUR_PFX_PASSPHRASE \

How to obtain token in forwarder.yml?

Discord Webhook

To get your Webhook URL, open your Discord and edit your channel. Go to [Integration > Webhook > Create Webhook > Copy Webhook URL]

Telegram BOT

To get your Telegram BOT token and Chat ID, please follow the following instruction.

1. Add @BotFather
2. Use /newbot command
3. Answer the questions, and you should have your BOT token.
4. Add @getidsbot
5. Use /start command
6. The ID under You is your chat ID.