Matrix-MTA

This script acts as a sendmail replacement to send email to a Matrix server, formatting the email content as chat message. It reads the email content from stdin, parses the subject and body, and sends the message to a specified Matrix room. If the room does not exist, it creates the room and invites the target user.

Requirements

Python3

Installation

Place the script matrix_mta in /usr/local/bin/matrix_mta and the configuration file matrix_mta.conf in /etc/matrix_mta.conf

Make the script executable.

Use the install.sh script to automate the placement.

sudo sh install.sh

System configuration

The script reads configuration from /etc/matrix_mta.conf, if available. Default values are provided for all configuration options. Set the required values to suit the proper Matrix server address and user credentials.

To use the script as a sendmail replacement:

On Linux systems, configure /etc/mail.rc

set mta=/usr/local/bin/matrix_mta

And create symbolic links

sudo ln -sfv /usr/local/bin/matrix_mta /usr/sbin/sendmail
sudo ln -sfv /usr/local/bin/matrix_mta /etc/alternatives/mail
sudo ln -sfv /usr/local/bin/matrix_mta /etc/alternatives/mailx

On BSD systems, configure /etc/mailer.conf

sendmail /usr/local/bin/matrix_mta send-mail /usr/local/bin/matrix_mta

Notes

On the synapse server it may be necessary to alter the configuration in homeserver.yaml to accept lower values for rate limits, allowing a faster stream of repeated messages to be sent. Be careful setting these on a public server which allows public registration and has many human users.

# Rate limiting settings
rc_message:
  per_second: 0.5  # Lower the per second limit
  burst_count: 5   # Lower the burst count

rc_registration:
  per_second: 0.1  # Lower the per second limit for registration
  burst_count: 5   # Lower the burst count for registration

rc_login:
  address:
    per_second: 0.1  # Lower the per second limit for login
    burst_count: 5   # Lower the burst count for login

  account:
    per_second: 0.1  # Lower the per second limit for account
    burst_count: 5   # Lower the burst count for account

rc_admin_redaction:
  per_second: 0.1  # Lower the per second limit for admin redactions
  burst_count: 5   # Lower the burst count for admin redactions

rc_joins:
  local:
    per_second: 0.1  # Lower the per second limit for local joins
    burst_count: 5   # Lower the burst count for local joins
  remote:
    per_second: 0.1  # Lower the per second limit for remote joins
    burst_count: 5   # Lower the burst count for remote joins

Testing

The functionality can be tested by passing the test email file to the script

cat test-email.txt | /usr/local/bin/matrix_mta

By calling sendmail which should point to the script

echo "Subject: Test Email\nThis is a test email body." | sendmail -v recipient@example.com

By utilizing the mail binary which should also point to the script