Scripting/PRFing POP3 server change to users accross a domain

Hey all.

I'm sort-of administering a network of around 70 users. Almost all of them
have Exchange, however, the Exchange is currently only used as an SMTP and
to store messages. Users' Outlooks pull emails from remote POP3 server.

Recently, I discovered I needed to change the POP3 and SMTP server addresses
for the users. Now, I've read of several options to do this (including using
a PRF file or scripting a change to the registry).

Does anyone know of a relatively sane way to make this change? If it's a PRF
or a script I would probably push the change through GPO, however, I am
totally lost regarding the move itself.

Any help would be greatly appreciated.