Majordummo

... is a group email tool for small, private mailing lists. View it as one step above a long CC: list.

It's designed to integrate with an existing mail delivery agent (e.g. a Postfix installation) and was made because Postfix can almost, but not quite, do exactly what I want already.

Prerequisites

Python 3.6 or above

Majordummo is implemented as a single file written in Python with no external dependencies.

Features

Accepts mail
Resends it to a list of people
Drops emails if they're sent by non-members (optional)
Rate-limits individual posters
Adds Reply-To header (optional)
Writes messages and delivery status to the filesystem
Logs everything
That's it

Majordummo has no cronjobs or daemons, and only runs when the MDA invokes it to process mail sent to the list. It will only ever send email to the list of recipients which is set in its configuration file -- it doesn't, for example, send bounce messages. It's configured using a JSON file and has no GUI.

Installation

After creating a configuration file, create an account, or virtual alias, for the mailing list name, and set deliver.py to run when mail is delivered to that account.

There are plenty of ways to do this. For example, you could "|/path/to/deliver.py --config /path/to/config" in /etc/aliases, or you could run it as part of a set of Procmail rules, or you could configure the Postfix pipe delivery agent to backend on to it, or...

Configuration

Configuration is supplied by a JSON file. Majordummo has a very minimal configuration, but you will probably want to change all of it. Copy config-example.json to config.json and customise it. Fields to change:

recipients: The people on your list.
reject_non_recipients: messages from non-list members will be dropped. The sender will not be notified, but the action is logged. Recommended.
set_headers: A list of headers to replace (if they exist) or add (if they don't) to outgoing messages.
db: Location of the database used to store rate limiting information.
per_user_ratelimit_secs: The minimum time in seconds allowed between posts from the same user to the list. Indended to stop mail loops, not hyperactive humans.
archive_dir: A directory name to write emails and delivery status. Can be set to null if you don't want archives.
smtp: Mail server details. You will want to change mail_from.
logging: A Python logging configuration -- note that logging/handlers/file/filename is a filename to write logs to.

Make sure you've set archive_dir, db, and logging/handlers/file/filename to valid paths which are accessible by the user running deliver.py (see "Running as a different user").

Running as a different user

Because it writes logs and archives emails, It's convenient to have majordummo run as its own user. I do this using a suid wrapper binary, but you can also do it by setting up a sudo rule and including sudo in your alias, or by using something like procmail.

Testing

When testing, it's best to set the list of recipients in your config to just yourself.

Testing can be split into two parts: 1) does my configuration do what I want? and 2) does my MDA correctly invoke majordummo?

You can test the configuration by running deliver.py directly with an email:

python3 deliver.py --config /path/to/config.json <email.txt

If that works, then send a test email to the list. Your MDA will log message delivery, so check those logs first. After that, check the log file you've configured in your config.json.