Click the Tools menu, and select Account Settings...
On the E-mail tab, select your POP account and click Change...
Change the following fields:
Click the More Settings... button
Select the Outgoing Server tab.
Verify the box next to My outgoing server (SMTP) requires authentication is checked and select Use same settings as my incoming mail server.
Click the Advanced tab, and Click the Use Defaults button
Verify that the settings were reset to the following:
Click Next, and then click Finish.