SSL or Certificate Authority in Exch 2K

Hello,

I would like to know if anyone would be able to advise me on how to secure my Exchange 2000 communication. I understand there is an option of using CA in Windows 2000 — how do I set this up?

Alternatively, what about SSL — is there additional cost involved ie. hardware or some sort of subscription with a third party required?

Do I need to run anything on the clients?

Appreciate any feedback from anyone.

Thank you,
Joyce