Deanafleschner said

I have used all of the setting that Godaddy and Thunderbird tell me to but I still get this error: The RETR command did not succeed. Error retrieving a message. Mail server pop.secureserver.net responded: unable to open that message

I had this problem too a few weeks ago. GoDaddy (GD) tried to help but they do not support TB. I then discovered that there was an email in my GoDaddy Webmail inbox that was causing the problem (failure to download the messages in GoDaddy to my computer TB inbox). Go into your GD inbox and view the emails and see if one is suspicious and/or it will not open. Delete it to trash. If that does not work, create a Save folder in GD and move all of the emails to the Save folder. One by one, then move them back into the GD inbox and see if they get automatically forwarded to your TB inbox. The email I had received was from a known person / company, but the email was generated from some kind of software he uses which apparently encodes something not compatible with GD and/or TB.

Deanafleschner said

I have used all of the setting that Godaddy and Thunderbird tell me to but I still get this error: The RETR command did not succeed. Error retrieving a message. Mail server pop.secureserver.net responded: unable to open that message

I went through all emails and found one that wouldn't open. I deleted it and all is great now! Thanks !!