Disclaimer In Exchange 2k3

We have been tasked with adding a corprate wide email disclaimer to all outgoing email. I have found a few 3rd party programs what will do this, but so far has been really expensive. Has anyone here had any experiance with this?
My task:
To impliment a disclaimer on all outgoing mail pop3 accounts. Using Exchange 2003. Clients using outlook 2k3, 2k, and a few older ones as well.

I have read that you can create a sig file for each person, but that is not really an ideal fix. Can this be done though Group Policy, or is there a setting in Exchange 2k3 to do this easily?
Thanks
SW