How to use Dynamic DNS with home server for mail, web?

Hi. I have a home router with (obviously) a dynamic IP. If I were to deploy a router (perhaps in the DMZ or via port forwarding), how do I configure it and a dynamic DNS service, so that I can receive email via my domain name, via MX records pointing to my server (sending will be authenticated SMTP to my ISP's server, I ume) and also that Web access will point to my home server also? I am not sure what to do because obviously the IP address will change, and yet all the A name, C name, MX records stuff use IP. Or *must* I use a fixed IP and there is no way to use dynamic IP for this stuff?