I need to set up an email discussion list for a small company. Ideally we'd be able to run three lists: directors, shareholders and general users.

We've tried a few Slack like things in the past but most of these people aren't into technology, and would prefer to just use email, but with the ability to send messages to a single address for distribution to the desired group.

Mailman does almost exactly what I need but has a reputation for being hard to set up.

I'd prefer not to use a commercial hosted system, but if it was cheap enough I'd consider it.

Does anyone have any ideas on the easiest, cheapest way to get something like this going? Anyone with experience running Mailman on Docker on a Digital Ocean droplet, for instance?