This article explains how to automatically delete old email messages from a folder or an entire account in Mozilla Thunderbird 68 or later on Windows 10, 8, or 7; Mac OS X 10.9 or later; and GNU/LINUX.
STOP Thunderbird downloading thousands of old emails!!
You can configure Thunderbird to automatically delete old messages in any folder in Mozilla. What's handy for Trash folders is also great for RSS feeds, for example.
Right-click on the desired folder.
Select Properties from the menu.
