If your aMozilla mail user, and your Thunderbird not downloading new emails or sending them to the receiver, then you have to change the Windows Firewall Configuration on your... moreIf your aMozilla mail user, and your Thunderbird not downloading new emails or sending them to the receiver, then you have to change the Windows Firewall Configuration on your system by following the below mentioned settings:1) Go to the below left of your windows system & search for "Firewall"2) Open the Windows Firewall and choose the settings to allow apps through the Firewall3) Then, click on the Thunderbird mail from the app list and you're good to go!!