Free mail list servers?

[Hewitt Tech]

A business group that I belong to wants to be able to use a mail list
server. I know that Yahoo provides a free list server but was wondering if
anyone knew of any others. Yahoo pays for their "free" servers with
advertisements that get attached to each message. Worse, they make you sign
up for their service and of course they get more info than one might want to
give. Any ideas?

-Alex