Conflict with Dial-Up Networking&Outlook

I am currently having a problem with my IP (Earthlink) being able to obtain a connection. I am able to connect with another. I have uninstalled & reinsalled Dial-up networking, Modem Drivers, and Outlook. Each time it will allow me to initially connect through Earthlink but once I open Outlook to get e-mail it creates a problem and the next time I attempt to log in it will not allow me to and provides and Error 678 or 650. I have spend many hours on the phone with tech support and am about at the end of my rope. Any suggestions?
THANKS!