Susie,

Within OE, you should be able to open up Tools/Internet Options/Accounts and change the settings for SMTP.
Insure that any additional email accounts (identities) have the spelling corrected as well, since Avast will use one SMTP server address to send mail for all accounts.

Make sure that you use the Apply button if available, then the Open button. Sometimes…just clicking the Open button does not “afix” the change.
When done, reboot computer.

Apparently, the configuration is in error. This could be caused by the MPW (Mail Protection Wizard) or simply a glitch running around in the computer. No matter, you can reconfigure it and it will be fine.

Earthlink MUST be spelled correctly for the authentication to take place.

Any further problem, let me know and I will walk you through it.

Take care.