My comment may not relate, but I'll share: posts from several others indicate that Godaddy has switched to Exchange for serving office365 accounts. Please check to see if that applies to you. If so, you will need Exchange support. There are two addons (OWL and EXQUILLA) that do that and they do it quite well. There is also a freeware app, Davmail, that does it well.

SOLVED....This was perplexing because it happened overnight and only to the Email accounts connected through GoDaddy, older Webmail Accounts that were migrated over to Microsoft.

After an hour and six minute wait I got through to GoDaddy and the less than helpful person told me uninstall and reinstall Thunderbird. While on hold I started digging through the internet.

Bottom line I only needed to change the Authentication settings to Oauth2 and it worked.

Sending also required a port change to 587.

Seems like GoDaddy should have known this.

I agree.

Looked up Davmail and saw pages about it however looks like from years ago and then the links were dead. Sad thing for me on the OWL/Equilla Apps is the support in my case. Installed trial, it worked, payed about $12 for a 49 week license (go figure) and product stayed in trial mode. Went through their online support and saw things that maybe I did wrong on install so I purchased a 2nd license directly from the pc's thunderbird and once again, failed. I went to paypal requested refund and got a snarky email back blaming me for my problems and admonished for not waiting 7 days for a fix on a business email pc. lol Through emails back and forth (which they had time for) I received credits for both purchases but they had NO TIME to address my problem. I looked for an alternative app and sadly there isn't one so I guess for me it's purchasing Outlook for my customer and be done with it. Sad

Changing the Authentication settings to Oauth2 and sending also required a port change to 587.

Doesn't work on my pc.