People keep mentioning Google Groups. I've been using it at everywhere workplace I can think of, since many years. Most internal mailing lists get set up via it. Did it use to do more?
However the web interface and search results are a true PITA. Waiting for the page to load just to jump to a random point in the page takes in the order of 5+ seconds on my system.
I remember the first iteration of groups was almost pure html and insanely fast. Like with most google products, it has been bloated to death.
They later added their own group stuff to it, and google group search became this weird mismash between the two. Searching usenet was easier and faster 10 years ago.