You mention POP account. Are you aware that gmail are stopping the use of 'less secure apps' ? You will need to make changes to Authentication Method. Thunderbird has made alterations so now both POP and IMAP accounts can use OAuth2 for gmail. Select 'Menu app icon' > 'Preferences' > 'Privacy & Security ' Under 'Web Content' * Select 'Accept cookies from sites' It may also be a good idea to make exception: * Click on 'Exceptions..' button * Enter: https://accounts.google.com * Set to 'Allow' * click on 'Save Changes' Now make changes to Account Settings: * Right click on gmail pop/imap account name in Folder Pane and select 'Settings' This opens the Account Settings in new tab The pop/imap account name should be selected Look bottom right for Outgoing Server (SMTP) * Click on 'Edit Server _SMTP' button * Set Authentication Method : OAuth2 * Click on OK Now set the incoming authentication: * select 'Server Settings' for gmail account * Set Authentication Method : OAuth2 Exit Thunderbird and wait a few moments for background processes to complete Start Thunderbird Gmail will prompt you to enter gmail email address and normal password you use to access webmail account. Follow instructions. It will ask this to allow Thunderbird to access server. An Oauth token will get stored in Thunderbird - same place as passwords and from then onwards Thunderbird will use it to access server.

Thank you Toad-Hall!