Thank-You so much for your time and effort. I really appreciate it. Please close this thread. Bye

Could you please do the following?

1. Open the menu > Help > Troubleshooting Information, then click Copy text to Clipboard.
2. Go to https://pastebin.mozilla.org/, paste the clipboard by right clicking in the large text area, select paste from the menu, change the retention period to expire in 21 days, use the Paste Snippet button to create a page containing your info, then copy the resulting URL (address) of the page created.
3. Open a reply to this post, and paste the URL to your troubleshooting information you just copied.

I have no idea how to use Thunderbird Troubleshoot Mode

This is not an acceptable response. No one is asking you to do more than provide the information and without it, clearly this topi is going no where. So I have rephrased the request with step by step instruction. Perhaps use them ig the first request was to complicated.

https://pastebin.mozilla.org/R80vCnZn

Matt, do you have an idea of what is happening?

David- I'm having an almost identical problem- getting the same error message, but trying to set up a netzero account. (I've been using Firefox for a couple years and love it, BTW, having no problems whatsoever!) Anyway, I was trying to take your suggestion to delete the account and start over, but can't figure out how. I've been sick so I'm a little slow on the draw, I'm considering just doing an uninstall, and reinstall. I don't have anything to lose at this point... But if all I need is to figure out how to delete the account I'll try that first. Thanks

To remove an account, - click account settings - highlight the account name on left side - scroll down slightly to 'account actions' - click there and select 'remove account'

Ok. Deleted account. Tried it again. It looks like it doesn't like my password, even though I've verified that I'm using the right password by logging in directly to the NetZero website. I re-entered the account info, left the password box blank, and unchecked the "remember my password" box. I typed a test message from that account to another email, and I got prompted to re-enter the password, but still a no-go. Grrrr!! And now, my test message has vanished, not in my sent box, can't find it anywhere! Where do I go from here?

Been waiting quite a while for a fix. I’ve been trying to add the account off and on for a long time. No go. I was able to add the email account to my iPhone and iPad Don’t know if that helps but I thought I would mention it.