If you got hacked then you first need to check your computer does not have any virus or program running which is collecting keystrokes from your computer. * Exit all programs. * Restart computer in 'Safe Mode' * Run full scans. If all is ok, then... * Logon to your gmail webmail account via a browser. You need to be able to establish access your webmail account first in order to get any imap or pop account to get access to server no matter what email client you use. If you can access gmail account via webmail then reset the password. In webmail account check you have selected the options for pop or imap as required. * In webmail - Select 'Settings' and then 'See all settings'. * Click on the Forwarding and POP/IMAP tab. * Make sure Pop and or imap is selected. More Info: https://support.google.com/mail/answer/7104828?hl=en-GB '''On computer''' Access Firewall (It might be the default hat came with computer or comtrolled by an Anti-virus product you installed) - make sure Thunderbird is set up as allowed program. If you are running a VPN then gmail server will not like it, so either disable the VPN or create a split tunnelling and set up Thundrebird to use it. If you are running any program that uses the localhost - typically anyone managing a website may use a program that uses localhost eg: Apache Xampp - then switch it off until Oauth has been set up. In Thunderbird * Settings > Privacy & Security Web mail section * Select 'Accept cookies from sites' * Accept third party cookies 'always * click on 'Exceptions' button * Add this: https://accounts.google.com * Set Status as 'Allow' * click on 'Save Changes' Then scroll to passwords section * Click on 'Saved Passwords' * Click on 'Show Passwords' You may get asked for a password. If you had previously set up Primary Password then enter that password Otherwise you will prompted by Windows Security to enter password - it wants the password you use when you start computer and enter password to access User Account and desktop. Remove all lines for passwords to do with the gmail account. Then check you have Correct server settings: In 'Account Settings' * Select 'Server Settings' for gmail account POP * server settings : pop.gmail.com * Port: 995 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * Username = full gmail email address IMAP * server settings : imap.gmail.com * Port: 993 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * Username = full gmail email address SMTP: * server settings : smtp.gmail.com * Port: 465 * Connection SEcurity: SSL/TLS * Authentication Method: Oauth2 * Username = full gmail email address Restart Thunderbird At gmail prompt enter password then select to allow Thunderbird access to server.