1. Check Firewall which may be controlled by an Anti-Virus product. Thunderbird program must be set up as an allowed program, otherwise the Firewall may block access to the ports it uses. Exit Thunderbird first and then set up to allow in Firewall. 2. If you accessed your webmail account and set up to use '2 step verification and an app specific password then you cannot use 'Authentication Method: Oauth2' - so Either switch the 2 step off in order to use Oauth. OR keep using 2 step and in Thunderbird use 'Authentication Method: Normal Password' for incoming and smtp and use the app specific password. 3. If you have a VPN switched on (I discovered my AV had auto switched on a VPN an dit caused issues) - switch off VPN as servers think t someone trying to hack your account so they block access. 4. If you have something using the localhost such as Apache Xamph then switch it off whiclst you are setting up the accounts that use oauth. Both gmail and hotmail now use 'Authentication Method = OAuth2' for both receiving and smtp. 5. This means in Thunderbird you must set up to allow cookies and remove any previously stored passwords. * Settings > Privacy & security * Under 'WEb Content' * Select option to 'Accept cookies from sites' * Click on 'Exceptions' button and set up to 'Allow' the following: * https://accounts.google.com * https://login.live.com * also make sure to add outlook.com, hotmail.com and office365.com * Then scroll to Passwords section * click on 'Saved passwords' * Remove all passwords. Exit Thunderbird and allow a few moments for background processes to complete. 6. Now add the accounts. When you get the prompt for password in a browser looking window please enter the required password for the account and follow instructions to set up an Oauth token which gets stored in the Password Manager. '''Server SEttings for gmail:''' IMAP server * Server name: imap.gmail.com * Port: 993 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * User name = full email address SMTP * DEscription : full gmail email address which is the same as the user name * Server name: smtp.gmail.com * Port: 465 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * User name = full email address '''Server SEttings for outlook/hotmail:''' IMAP server * Server name: outlook.office365.com * Port: 993 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * User name = full email address SMTP * DEscription : full email address which is the same as the user name * Server name: smtp.office365.com * Port: 587 * Connection SEcurity: STARTTLS * Authentication Method: Oauth2 * User name = full email address Additional helpful Help Article: https://support.mozilla.org/en-US/kb/microsoft-oauth-authentication-and-thunderbird-202