Comment 32 for bug 1853007

I consider this a memory leak and/or design flaw. My feeble understanding of Thunderbird innards suggests that these files might be created to form the final message that is sent? If so, they should be deleted once the message is sent and the copy is in the Sent folder. They should exist only on the POP or IMAP server and ~/.thunderbird. Use of the file system should be restricted to the user's ~/.thunderbird folder, then deleted when finished. I don't know where the files appear on Windows 10, but in any case, delete any temporary files you need to create.

In case the system crashes or is shut off while Thunderbird is active, the next time Thunderbird gets launched those temporary files from the previous session could be used to reconstruct the interrupted message, should the user wish to retrieve it. The current design places permanent files in a location meant for temporary files.