first make sure ESET is not monitoring your Thunderbird profile folder. You press delete, the file is updated, Eset scans the file, you click delete and repeat, but that sequence might be falling over itself. EST is not known for it's speed. I dropped it in favor of defender 2 years ago because is had become a slug. So old school time. Windopws has some useful shortcuts. I have been using that since the early 1990s. List can be controled with both the mouse and the keyboard. Ctrl+A selected everything in a list. 50,000 emails in a list. Not an issue. After you select something, holding the shift key allows ever everything between the selected item and where you click next to be selected. The next adjunct to that is holding the Ctrl key while clicking. This reverses the selection status of only the list item clicked. Using these techniques together can allow for huge list with many personalizations to select or unselect items to be managed. In this case with a press of the delete key to get all selected items deleted. You could also use the little widget above the up down slider to customise the list headings to include "select messages" that puts a web page style select box beside each entry. Apparently introduced for "accessibility" but personally I think it is to cater for a community of folk that only know how to use web pages, but are actually not familiar with the use of a keyboard.