Was the error received when trying to send email from firstname.lastname@example.org to user@hotmail account? Can you send a test email from email@example.com to firstname.lastname@example.org?
What do you have as your username/password under Outgoing? On the screen you got the settings above, click "More Settings" in the bottom right, and then "Outgoing Server" tab and should see something like this:
It should be selected as shown above. I think right now it is set to a Hotmail email address. If so, you are trying to send email as a hotmail user over Cox SMTP servers, and when they relay the user/password, hotmail is saying it's wrong.
Was this orginally a Hotmail account that you changed the POP/SMTP settings of? If so, did the original Hotmail account use IMAP? If so, I would suggest creating a new profile in Outlook with your Cox email settings. You don't need to delete your current profile, you can just disable it from syncing.
Edited by Trikein, 02 September 2016 - 01:10 PM.