For a client we want to set up a email discussion list so users can email comments to a central address, but can also see each other's comments, etc. Our users are familiar with email but sending them to a forum is one extra step and from past experience they won't bother.
How does one do this, so that the email address used is belonging to their own web domain? Is it a piece of web software you just install on the web-server? All the ones I've used are open-source through sourceforge, etc, so how they work is hidden.
Ideally one which allows access through a web-portal as well would be great.