SEX! or, how do I mail to a lot of unix users?

[thermal%solgel.hepnet at CSA2.LBL.GOV]

I would like to be able to send a mail message to all the users on
a unix machine.  Of course, I could do it the long way, that is,
do a 'finger' or 'who', thus getting a list of all the users, and
then sending a mail message to each, one at a time.  Is there a
quicker way? (it seems to me there could be two or three different
ways, such as setting up a mailing list, or some nifty command that
will do this on one stroke of the finger).  Obviously, I'm not a
unix guru or wizard, so make your explanation understandable, please.

Thanks, Dana