With new installs, Gmail needs to re-authenticate. That's what it sounds like you're experiencing.

I am able to log directly into gmail with no problem, so I assume I'm authenticated?

I am able to log directly into gmail with no problem, so I assume I'm authenticated?

No. That just means you used a browser and logged directly into webmail. It proves your password worked to allow acess to your gmail account. It does not mean Thunderbird can access the internet nor does it mean the settings are correct.

It is likely McAfee will be controlling the Firewall. Exit Thunderbird Access Firewall Make sure Thunderbird is set up as an allowed program.

Do you have any VPN operating? Make sure it is switched off. Double check McAfee has not gone and installed a VPN.

Then start Thunderbird. Work through the following to ensure all settings are correct.

• 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'

Under 'Passwords' section:

• Click on 'Saved Passwords'

You need to remove any saved password that is used by the gmail mail account. It may display one or more lines relating to the gmail username/email address.

• Select the mailbox://(if pop), imap:// (if imap), smtp:// , oauth:// line
• click on 'Remove'.

Now check 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 - same as you used 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.