Outlook 2007. Can receive email. Cannot send. Small screen "Enter Netword Password" continously pops up. Hit delete and pops up again. Uninstalled Outlook and reinstalled...no luck. Ran Registry repair program...no luck. Spent 10 hours online with AT&T Connectech and they said Outlook corrupted. Installed new Outlook 2010, same issue. Uninstalled and reinstalled 2007. Same issue. FRUSTRATED!