This article will walk you through how to configure the Thunderbird email client to access your EarthLink email. Thunderbird is a full featured email client that also includes locally stored calendar and tasks features. Setup generally just required your email address and password, but there are a couple of manual setting changes you will need to make as well.
While Thunderbird handles most of the settings, you will need to make a couple of manual changes before you can start sending new email.
The following screenshots are for reference if you want to visually confirm your email settings to known working settings for EarthLink email.
Select the EarthLink smtpauth.earthlink.net (Default) option from the list and click on Edit.