re :I see that nicksasso21 may be having a similar issue (but with Office365), where you asked for the Access Error Code info,

In that error console information it said: mailnews.smtp: Command failed: 535 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant. Visit https://aka.ms/smtp_auth_disabled for more information.

The link mentioned in error console : https://aka.ms/smtp_auth_disabled That link goes to this location - I specifically include the info on 'enable smtp': https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission#enable-smtp-auth-for-specific-mailboxes

The user discovered they were not enabled for SMTP. After switching it on - all now works. So I managed to help them sort out their issue.

Let's recheck your errors again In Error console. After clearing and restarting thunderbird then do a send - but create a new write message - do not use a message presaved in drafts - do not save in drafts. Then check error console - upload an image.

I have not been able to get Thunderbird to work with my outlook.com email address. W10/32 bit fully patched Thunderbird 128.2.3esr (32 bit) POP Mail Server outlook.office.365.com, port 995

• • my "user name" which is my email xxxx.outlook.com

SSl/TLS OAuth2

• • In SMTP Server**

outlook.office365.com 465 SSL"TLS OAuth2 xxxx@outlook.com

I should have mentioned that I DO NOT have an office365 account.

Logging to www.outlook.com with my UN (=outlook.com email address) and password works. Although the lack of a way to turn off the MS spam filtering makes it useless. I have put some MS thing on my phone and I think I had to do some 2FA thing at least once when bringing up www.outlook.com.

I should have included that I DO NOT have an office365 account.

Help please.

Sorry for the delayed response, had to deal with loss of power and other minor damage due to hurricane.

I restarted Thunderbird, captured the Mail and News Account, cleared error code console, sent new email, which failed and ask to retry, I retried and failed, then cancelled the email. Here is the output from the error code console, as an image.

Thanks.

EDIT: Installed Win 11 on another computer, installed Thunderbird v128.3.0esr, let it automatically assign IMAP and SMTP (using my hotmail.com email creds). It assigned SMTP with outlook.office365.com (587, STARTTLS, OAuth2). It will not send email neither. In the error code console (see third image), there is an extra line, right after the initial 535 error, stating:

"Error during AUTH XOAUTH2, sending empty response"

I deleted, uninstalled, removed profile, reinstalled Thunderbird, manually used smtp.office365.com (OAuth2 was listed) with same result. I repeated this and then tried smtp.outlook.com, but OAuth2 does not show up in the pulldown list (same as on Debian).