Whether you need to block a domain address from sending junk mail or wish to block emails from a specific person, Mozilla Thunderbird allows you to create email rules to properly handle the email. These rules are also known as filters, as they continuously monitor your inbox and automatically remove the message from your inbox or server, depending on your filter settings.
Click "Tools" at the top of the Mozilla Thunderbird screen and click "Message Filters" from the drop-down menu.
Click the "New" button to create a new filter rule.
Type in a name for your filter in the blank field. Click the tabs under the "Apply filter when" section so that they read "From" "is," and type in the email address you wish to block in the blank field.
Click the "Move Message to" tab under the "Perform these actions" tab, and click "Delete Message" from the drop-down menu. Click the "OK" button.
Click the "is" tab and select "ends with" from the drop-down menu to block domain addresses. Type in the domain address in the blank field, such as "@gmail.com" or "@mac.com."
Click the "Move Message to" tab and select "Delete Message" or "Delete from POP server" from the drop-down menu. Click the "OK" button.