550 Error Message - Resolved
Got the problem fixed through Earthlink online tech support. This is what I was told to do.
1) Check the box that says "My outgoing server (SMTP) requires authentication" under internet email settings.
2) Check the box below that says "Log on using" then put user name and password. Now here is the confusing part. Under username, I was told to put my earthlink email address. This is not my username.
3) Under "Advanced" under internet email settings, I was told to change the 25 in the "Outgoing server" box to 587.
Hope this helps someone else.