I'm about to shut down my Exchange 5.5 server and switch over to my Exchange 2003 server. I'm curious as to what I'll need to tell my ISP when I do this. For example, lets say my current MX record says that "domain.com" points to IP address 10.11.12.13. Will I just need to tell them that I need all traffic destined for "domain.com" to be sent to the new servers IP address? Also, how long would a change like this take to propogate through the entire internet? Is there a way to avoid this downtime (propogation)?