Microsoft Account email addresses are called alias by microsoft. All email addesses need to use same password as the one used to access Microsoft Account login. One of the email addresses will be set up as 'primary'. If you have several email addresses and use a third party email client (Thunderbird) to download mail from all of them - you will find microsoft will only allow you to send via smtp using the email address set up as 'primary'. example: if you have a name@outlook.com email address and a name@hotmail email address and the name@outlook.com is set up as primary. In Thunderbird both mail accounts need to have the smtp outgoing server set up to use name@outlook.com The hotmail email address mail account will also need the 'REpy-to Address' set up as the hotmail email address. That means anyone replying will use the REplt to so email should end up coming into the correct account. On computer: '''Firewall''' Access Firewall and make sure Thunderbird has been set up as an allowed program so nothing will block anything. '''VPN''' Check computer for VPN - your Anti-Virus may have auto enabled one without you knowledge. Switch it off. Let us know if you switched it off. '''Localhost''' Do you use anything like Apache Xampp - typically people who manage websites may use similar products but they use the localhost. You must switch those products off because setting up Oauth needs to use localhost. You can switch on again after setting up oauth. In Thunderbird: * Settings > Privacy & Security * Web Content * Select 'Accept cookies from sites' I'm asuming you have already created the account and it's been ok for a while but have password issue. Or removed the account and are ytrying to add it again. * Whilst in Privacy & Security - scroll to Passwords section * click on 'Saved Passwords' * If you see any mention of the account username you are trying to fix password - select the relevant lines and click on 'Remove' * Click on Close Then exit Thunderbird- wait a few moments for background processes to complete and restart - it should force a request for password - enter email address and normal password and then you should be asked to allow Thunderbird. '''If you are trying to create a new account''' Switch off the following as it's still experimental. * Settings > General * Account Hub * uncheck this checkbox: 'Create accounts in the new Account Hub' Then create the mail account * Menu app > New Account > Email * Enter name * Enter email address * Enter password * Select checkbox to remember password. * Click on 'Continue' Thunderbird by default will look for the IMAP server settings. You should get a prompt. enter email address and normal password and then you should be asked to allow Thunderbird. This creates the oauth token.