Nstmp Folders In Thunderbird

I recently spotted two new folders in Thunderbird which I definitely did not create. The names of the folders where nstmp and nstmp-1 and they did contain mails from the main email inbox folder. That was strange on first sight because it was not obvious why those folders were created in first place.It turned out that Thunderbird had created the two folders during folder compacting.

Thunderbird is creating the nstmp folders when it is compacting folders. When Thunderbird is interrupted during folder compacting it will not delete the nstmp folders that contain the temporary emails of the process up to the point where the compacting process was stopped. Compacting will stop when Thunderbird is (accidentaly or due to a crash) closed during compacting or when a new email arrives during that operation.

Those nstmp folders can normally be deleted but a user should check the original folder to make sure that it still contains all the mails that are listed in the nstmp folder. If that is the case the folder can be easily deleted by right-clicking it and selecting delete from the context menu.