Retention setting execution

It seems like T Bird only executes my retention settings when I open a folder. For example, my Trash folder has 3.2 MB of mail and has a 3 day retention policy set. When I click on the folder, it starts removing emails beyond that time frame and now the folder only has mail within the three day window and has only 28.7 KB. My question is whether there is a setting that will change that so that T Bird executes the retention policy for each folder when I first open T Bird, rather than waiting until I click on the folder. Thank you