This will open an E-mail Accounts window,
Select your account in the window and click on Change.
On this window verify all information is correct. The User Name is your full email address. Click on More Settings...
On the Ineternet E-Mail Settings window click on the Outgoing Server tab.
Put a check mark in the box next to "My outgoing server (SMTP) requires authentication"
Make sure the dot below stays on "Use same settings as my incoming mail server"
With that done you can now click on OK.
You should now be back to the E-mail Accounts screen, click on Next and then click Finish.
That's it, You're DONE!