re :Normally a form should appear asking Mozilla thunderbird email wants to access That would mean you have created an imap account using Authentication Method : OAuth2 for both incoming and outgoing smtp server.

re :I have already set permission for less secure apps Not necessary if you have IMAP account using using Authentication Method : OAuth2.

For that Gmail login form to appear you need cookies allowed.

Check to see if you have cookies enabled. In versions prior to 78*:

• Select 'Menu app icon' > 'Options/Preferences' > 'Options/Preferences'
• In 'Options/Preferences' left Pane select Privacy
• Select checkbox 'Accept cookies from sites'

In versions 78* or later:

• Select 'Menu app icon' > 'Options/Preferences'
• In 'Options/Preferences' left Pane select Privacy & Security
• Select checkbox 'Accept cookies from sites'

then restart Thunderbird.

Hi, The configuration of cookies is correct. If I don't want to use OAuth2 how should I configure?

If I don't want to use OAuth2 how should I configure? In webmail account set to use 'less secure apps' In Thunderbird, Set 'Authentication Method' to 'Normal Password'