Microsoft made some changes so check out the following.

Micosoft now say all email addresses using Microsoft account are now called 'alias' accounts. They must be set up to use the same password as the Microsoft account. Those accounts may have a msn.com, hotmail.com, live.com, outlook.com or other email address using the office365 server.

Whatever account you set up as the 'primary' will be the only email address you can use for smtp outgoing mail no matter what other 'alias' account is receiving mail. But you can choose what you want to set up as 'primary'.

All of the above must be set in the Microsoft account webmail account accessed via a browser.

VPN Check computer to see if there is a VPN that's been enabled. Many Anti-Virus products now offer a VPN but servers do not like VPN as it hides IP so server will block access. Switch VPN off or create a slpit tunnelling and set up Thunderbird to use it.

Localhost If you use a product that uses the 'localhost' then you need to switch it off until Oauth has been set up. Some people manage websites and they might use eg: Apache Xampp and it uses Localhost.

In Thunderbird make sure cookies are allowed.

• Menu icon > Settings >Privacy & Security
• Web content
• Select: Accept cookies from sites and 'always' and 'until they expire'

IMAP settings

• Server name: outlook.office365.com
• Port: 993
• Connection Security: SSL/TLS
• User Name: full email address
• Authentication Method: OAuth2

Office 365 SMTP settings

• Description: full email address
• Server name: smtp.office365.com
• Port: 587
• Connection Security: STARTTLS
• User Name: full email address of whatever you set up as the 'primary' account
• Authentication Method: OAuth2

Other info that may be relevant: https://support.mozilla.org/bm/questions/1489736

Hi, So when I went to home yesterday, I was on my home network, so Thunderbird emitted a pop-up which asked for entering my password for authentication. When I entered that, I started receiving emails. I don't know why is that.

Today I am back to office, and again cannot get emails. For some reason it seems that that pop up needs to appear so that I can manually authenticate. What is happening and how do I then manually authenticate on office network?

Hi, there seems to be an issue with my office wifi. When I connect with VPN, I am able to authenticate. Sorry for the noise.