So it does not send. Is there an error? I am guessing there is but on a whole lot of words you failed to mention what it was.

If the SMTP server named XXXXX is associated with the Identity being used to send mail, Thunderbird will attempt to authenticate using that identity and the relevant token. Is Microsoft "Modern Authentication" incorporating oAuth2.0 broken? It might well be.

What I see far more of is folk with a single Outgoing server (SMTP) being used across multiple identities complaining that it only works on one of them.

I personally see no merit in removing an account and adding it again. If that fixes something your account settings were wrong and the issue could have been resolved much more quickly be correcting the settings. Without the risk of not being about to add it again. Common. Not being able to get the new account to work because the issue was not in the settings. Also very common.

Why delete the passwords? Oauth does not use passwords except when the initial authorization flow occurs and that is Microsoft asking you for your password, via a web page they serve from their web server, to authenticate the request for Thunderbird to access you mail. Thunderbird never actually sees you password in that process, let alone save it. Oauth uses tokens issued by, in this case by Microsoft, following the initial flow and updated by them periodically until they decide they need a new authentication flow to extend the authority of Thunderbird to connect. Depending on how you access their mail server that can be anything from almost daily (where VPN's are used) to like once a year. Last time I was asked was when Transferred my profile to a new computer a couple of years ago.

So did you delete the authentication tokens or you password? Whi9le both can be found in the password manager, they are not the same thing.

Hi Matt,

I thought, its a usual error thats why did not post the errors. But here they are as attached.

Firstly, I do not understand what do you mean by, "Is Microsoft "Modern Authentication" incorporating oAuth2.0 broken?" Where or how to find whether Microsoft "Modern Authentication" , is incorporating oAuth2.0? And I think this is the issue.

I am using, the following Thunderbird and it says its uptodate.

128.5.2esr (64-bit) Release notes Thunderbird is up to date

Yes, I can see deleting and adding as a new account did not do any change, since this was not a settings problem, which I can also see now. This is something to do with the connection between Thunderbird and the Microsoft server. Which to my understanding Thunderbird is not able to.

On the question of deleting the token or a password, I did delete the password and just checked now in the "saved passwords" the password for hotmail is not there.

So what is the solution? What do you think?

There are a whole raft of "usual errors" but it is much easier if we don't try and guess which applies.

You do not understand, and largely neither do I. There was a perfectly ugly authentication method for the web (oAuth2.0) and first Google and now just about everyone has force fed it for email to which it is only marginally effective. It forces mail clients to spawn a browser for authentication, hardly a specialty of mail clients. Thunderbird was luck being built on a Firefox platform had tested browser code handy. But it does significantly increase the surface area for vulnerabilities for all mail clients by virtue of it being browser based.

Mired Authentication is a term invented at the Redmond campus because they have to "innovate" every open protocol they ever use to put some proprietary code in there so they have an excuse for security through obscurity.

I do not think that is you issue however. please go to the outgoing server (SMTP) entry in account list in account settings.

Do you have more than one hotmail account listed. Perhaps even the same user name with different description. I am thinking you are sending via that server with an SMTP settings that use a password, not oauth and the connection is being refused.