I'm relocating my client's pages to a new server. Their old system was running Plesk and had some email groups and a few mail forwards defined. The new server has no Plesk and I'd really rather not install it just for the email groups either, so I'm looking for a new alternative for creating and managing the lists.
Their main site is going to run on Drupal 6.x, so a module for that would be the preferred choice. I tried searching for one myself, but to no avail.
Anything else that gets the job done will do as well, as long as the client who is not very tech-savvy can modify and add lists herself. The server is a Debian 5, root access is available.
Any suggestions are highly appreciated.