Thunderbird says "login failed" when trying to send an email

Microsoft stinks. That's why I am trying so hard to get Thunderbird to work. When I reply to an email in an email chain that I was the last to reply to, it responds to me. I need to reply to all, the remove myself. Thunderbird corrrectly responds to last person other than me.

I was downloading Office 365 before so I could try "Old Outlook". As I said, that failed. It worked today. Yay! I switched to the old layout. It's read only without a subscription. I had Office 2013. I have the codes, but it won't let me download it.

I think I will have to try Geek Squad again. Everything I search says it should work, but I have no idea how to find the setting.

You have been absolutely amazing. I don't know if you are a Mozilla employee, or just a very nice person, but I cannot tell how much I appreciate your help (and you keep some amazing hours on this forum... :) ).

Thank you.

I went to Geek Squad today. He said all the settings are correct. He found something with other people having the same issue. They said MS said they won't let it in immediately, but it should work in a week or two. I guess I'll find out.

That sounds very odd. The info below was sources from Mozilla blogs on this issue. Don't believe the word of a support rep over the phone as they are not engineering this protocol. Merely clearing the call que.

EWS (Exchange Web Services) email support has been available since Thunderbird 145, but Microsoft will shut down EWS for Microsoft 365/Exchange Online by Oct 2026 and will require switching to Microsoft Graph API

If you are connected via EWS to Microsoft 365, you will need to set up a new Microsoft Graph account before the shutdown.

Use the Correct Account Type

When adding your account:

   In Thunderbird, go to Menu ☰ → New Account → Email.

   Enter your Microsoft 365/Exchange email address and click Continue.

   Sign in via the Microsoft OAuth panel (do not type your password in Thunderbird).

   When prompted, choose Exchange or Microsoft Graph API (Graph is required for Microsoft 365 after 2026) 

   In short: For Microsoft 365/Exchange Online, Thunderbird now prefers the Microsoft Graph API over EWS. If you are blocked from Graph or your org still uses EWS, ensure you have Thunderbird 157+, update your account type, and use the official Microsoft OAuth sign‑in. For on‑premises Exchange, EWS will remain supported until 2027 Mozilla 

I hope this helps. You need to create a new password Somewhere.

We deleted the account and entered it again. At a point when sending an email it asks me to enter a password. When I click the button, Chrome opens and flashes, but stays on the webpage it was on. The first agent I spoke with a few days ago went somewhere and hit reset, and it then opened a page for me. No one since that person has been able to find that page.

I just changed my default browser to Edge and it does the same thing.

Thunderbird fills everything in for me. Where can I change it? Is it on that page I can't see?

Yeah I'd have to remote you at this point lol Good morning look in your browser settings on the spoked wheel page settings. Scroll to content settings and manage. Make sure you're allowing everything. I don't know if you have a third party pop-up blocker running in the system tray as an add-on in your browsers etc but yeah you're blocking it on your end.

But you're on the track that is what you need to do to get your emails to work you need to create a new profile and password. As far as your system is concerned with ad blockers whatnot that's something you will have to configure I don't even see a screenshot of your desktop at this point it is kind of difficult for me to guess

I steered you in the wrong direction on your settings by the way you want to click on the three dots at the top of the edge browser look into settings and then over to cookies and site permissions manage your extensions as well you may be blocking site redirects and that's why the page isn't displaying properly.