Simply put here's what you need to do.
1. Rerun connect to intenrt wizard on SBS 2008. If you have SBS configure your regristrar's settings and router then it will handle steps 2-3 below otherwise do them manually.
2. Verify router/firewall settings to make sure your new public ip gets through to your mail server. Depending on how your are set up i.e. how many public ips you have/port mapping/passthrough etc.
3. Update A record on remote.yourdomain.com to new ip of your SBS 2008 server (assuming it's the one handling your mail). While your at it, check your SPF record.
4. Contact your new isp and have them configure your reverse dns to remote.yourdomain.com (change remote to whatever you are using)
5. test your mail and remote web workplace.
6. and for good measure wouldn't hurt to run the BPA again.
