mail forwarding / MX records

[grahamet]

I need to forward all of a clients mail to a different mail server as they want to pick their mail up via their ISP's SMTP server.
The web site needs to be on my server.

I the mail servers for the ISP are punt-1.mail.demon.net and punt-2.mail.demon.net.

What zone records do I need to change or set up to acheive this?

Please say it slowly I'm not so smart

Thanks