M2MB is a smtp server that doesn't send mails (!) but transfer the message to a Slack/Mattermost instance through a webhook.

By default, m2mb will send all mails to the default configured channel. You can configure another default channel in the command line (see --help) or configure per-mail rules using sieve filters (see documentation).

You need python 3.6 to use this program. If you can't install python 3.6 on your system, there is a Docker image available on Docker Hub

$ git clone https://github.com/thperret/M2MB
$ pip install --process-dependency-links .

$ docker pull thperret/m2mb

$ m2mbd localhost 8225 https://mattermost_instance/hooks/randomid

$ docker run -e WEBHOOK_URL=https://mattermost-instance/hooks/randomid -p 8225:25 thperret/m2mb

For advanced use, see documentation.