Telegram to SMTP

A Telegram Bot that forwards chat massages and files as emails. Works in private chats, groups and channels.

This bot is only capable of forwarding text messages, polls, locations, photos, documents, audio files, video files, voice messages, stickers and video notes.

Use Case

Some of our club members refuse to join the club's private information broadcast Telegram channel. The organizer had to write each message twice. One for Telegram and one for email distribution. This bot fixes the problem by simply sending Telegram messages to a mailing list.

Installation

Requirements

• Java 11
• Docker Runtime (alternative)
• Docker Compose (optional)

Instructions

1. Create a new Telegram Bot using the official Telegram BotFather and note the Bot's username and HTTP API Token.
2. Invite your new Bot into the chat of your choice. Your Bot must have just enough permissions to read chat messages.
3. Retrieve the ID of the current chat.
   1. Send any message to the Telegram chat (or group or channel)
   2. Open https://q3qkk.csb.app/ and paste the Bot's token into the input field

The tool extracts the chat ID from the returned JSON response. Note down your chat ID.

Alternatively, if you don't want to use an untrusted tool, you can visit https://api.telegram.org/bot${token}/getUpdates and replace ${token} with your HTTP API Token. Find the number where it reads [...]"chat":{"id":>someNumber< or

{
  "ok": true,
  "result": [
    {
      [...],
      "message": {
        [...],
        "chat": {
          "id": >someNumber<, ← that is the number you want
          [...]
        },
        [...]
      }
    }
  ]
}

Deployment

The Telegram Bot you have created is just a gateway between Telegram and the actual Service Tg2SMTP. You must start this service in order to retrieve messages and send emails. You'll probably want to run Tg2SMTP on a server either way to guarantee mails get sent instantly.

There are two ways:

1. The traditional and probably most common way is to start the executable .jar-file and
2. a more manageable method using Docker.

Configuration

Before you can start you should know your SMTP provider's hostname/server address/SMTP server, port and authentication mechanisms and constraints as well as your login credentials. Most providers provide a FAQ for common email clients like Outlook, Thunderbird etc.

The following table shows all available configuration properties. Choose either Property or Environment Variable column depending on your deployment method. Spring, the underlying framework, allows a deployment method independent way to provide configuration for Tg2SMTP. To do this, write the desired configuration key-value pairs in an application.properties or application.yml file and place the file next to the .jar file. Spring then reads this file at startup.

Property	Environment Variable	Datatype	Default Value	Example Value	Description
tg2smtp.notification.subject	TG2SMTP_MAIL_SUBJECT	String		"[Telegram] New Message"	The mail's subject line
tg2smtp.notification.to	TG2SMTP_MAIL_TO	String[]		john@example.com,jane@example.com	Comma-separated list of zero or more mail recipients
tg2smtp.bot.chat-id	TG2SMTP_CHAT_ID	Number[]		1337420,-0815	Comma-separated list of zero or more authorized Telegram Chat IDs
tg2smtp.bot.username	TG2SMTP_BOT_USERNAME	String		MyAwesoneTg2SmtpBot	The Bot's username
tg2smtp.bot.token	TG2SMTP_BOT_TOKEN	String		XXXXXXXX:YYYYYYYYY	The Bot's HTTP API Token
tg2smtp.messages.active	TG2SMTP_MESSAGES_ACTIVE	String[]	ALL	TEXT,PHOTO,LOCATION,VIDEO_NOTE	Comma-separated list of Telegram message types1.
spring.mail.host	MAIL_HOST	String	localhost		The SMTP server that is used to send mails
spring.mail.port	MAIL_PORT	Number	587		The SMTP server's port
spring.mail.username	MAIL_USERNAME	String	smtp@example.com		The SMTP username for authentication (required if smtp_auth is active)
spring.mail.password	MAIL_PASSWORD	String	d3v		The SMTP password for authentication (required if smtp_auth is active)
spring.mail.properties.mail.smtp.localhost	MAIL_HELO	String	localhost		The well known hostname Tg2SMTP is running on (optional2)
spring.mail.properties.mail.from	MAIL_FROM	String	smtp@example.com		The email address mails are sent from (optional while smtp_auth is active)
spring.mail.properties.mail.mail.reply.to	MAIL_REPLY_TO	String			Email address the recipient should answer to (optional)
spring.profiles.active	SPRING_PROFILES_ACTIVE	String	smtp_auth,smtp_tls	smtp_auth, smtp_tls, smtp_auth,smtp_tls or none	Comma-separated list of active Spring profiles (optional)

Both profiles, smtp_auth and smtp_tls, are active per default, as it is the most common authentication mechanism throughout.

Message Types

This bot will only forward these messages as stated in the introduction. For the sake of completeness the following list shows the available messages types and their activation key.

Message Type	Configuration Key
Text Messages	TEXT
Locations	LOCATION
Polls	POLL
Photos	PHOTO
Documents	DOCUMENT
Audio Files	AUDIO
Voice Messages	VOICE
Video Files	VIDEO
Video Notes	VIDEO_NOTE
Stickers	STICKER

Jar

Download the .jar-file of the latest release. Execute the following command in your console to start Tg2SMTP. Don't forget to replace the sample configuration with your own.

java -jar tg2smtp-1.0.0-rc-1.jar \
 --tg2smtp.notification.subject="[Telegram] New message" \
 --tg2smtp.notification.to=john.doe@example.com,jane.doe@example.com \
 --tg2smtp.bot.chat-id=1337420 \
 --tg2smtp.bot.username=MyAwesoneTg2SmtpBot \
 --tg2smtp.bot.token=XXXXXXXX:YYYYYYYYY \
 --spring.mail.host=smtp.example.com \
 --spring.mail.port=587 \
 --spring.mail.username=user@example.com \
 --spring.mail.password=s3cr3t \
 --spring.mail.properties.mail.smtp.localhost=my-host.example.com \
 --spring.mail.properties.mail.from=user@example.com \
 --spring.mail.properties.mail.mail.reply.to=no-reply@example.com \
 --spring.profiles.active=smtp_auth,smtp_tls

Pass --spring.profiles.active= if you want to deactivate SMTP authentication and SMTP transport TLS encryption.

The configuration arguments above are not necessary if a configuration file is in the same directory.

Docker

Replace the sample configuration and run the command below to start a Tg2SMTP Docker Container.

docker run -d \
 -e TG2SMTP_MAIL_SUBJECT="[Telegram] New message" \
 -e TG2SMTP_MAIL_TO=john.doe@example.com,jane.doe@example.com \
 -e TG2SMTP_CHAT_ID=1337420 \
 -e TG2SMTP_BOT_USERNAME=MyAwesoneTg2SmtpBot \
 -e TG2SMTP_BOT_TOKEN=XXXXXXXX:YYYYYYYYY \
 -e MAIL_HOST=smtp.example.com \
 -e MAIL_PORT=587 \
 -e MAIL_USERNAME=user@example.com \
 -e MAIL_PASSWORD=s3cr3t \
 -e MAIL_HELO=my-host.example.com \
 -e MAIL_FROM=user@example.com \
 -e MAIL_REPLY_TO=no-reply@example.com \
 -e SPRING_PROFILES_ACTIVE=smtp_auth,smtp_tls \
 kchwr/tg2smtp:latest

The example/ directory contains a Docker Compose file that configures Tg2SMTP the same way as the example above.

Docker Swarm Mode users may configure their stack using Docker Secrets. Just append _FILE to the appropriate environment variables: MAIL_USER_FILE, MAIL_PASSWORD_FILE, TG2SMTP_MAIL_TO_FILE, TG2SMTP_CHAT_ID_FILE, TG2SMTP_BOT_USERNAME_FILE, TG2SMTP_BOT_TOKEN_FILE. Keep in mind that only one Tg2SMTP instance with the same username can register at the Telegram Bot API concurrently.

Development

Requirements

• Java 11
• Maven 3.x
• Docker Runtime
• Docker Compose

Configuration

This project already provides sane defaults to configure Tg2SMTP properly. You may override these values to match your preferences. To do so, create an application.[yml,properties]-file in your project root and override the properties you want to configure.

Use the debug profile to disable the email sender and log incoming messages to the console. Downloaded files will be stored in data/downloads.

Setup

It's also a good idea to download dependencies and build the executable .jar-artifact once before you start hacking.

mvn package

Start a development SMTP server on your host for easier development. Received messages are stored in data/received-emails/.

docker-compose -f docker-compose.dev.yml up -d

To stop the stack use the command below.

docker-compose -f docker-compose.dev.yml down

Usage

Run Tg2SMTP by calling the command below. Depending on your environment and preferred IDE you can start the main-class or main-method directly from your IDE.

mvn spring-boot:run

Licence

Apache License 2.0 - Kammerchor Wernigerode e.V. - Built with ❤️

Footnotes

1. Use ALL to forward all compatible messages or select the type of message you want. ↩

2. Depends on the provider if the HELO header is necessary, but might resolve issues anyway if set ↩