Im using Thunderbird Beta release. Starting last week, my PC would become extremely slow, to the point it would nearly come to a complete halt. After digging around, I realized it was due to excessively large Thunderbird NSTMP files that were being created. I would delete them and the speed would improve. But then a while later, the NSTMP files reappear and gobble up all my Harddisk again. Part of the issue is the sheer large size of the file, which will consume all available space on my HD, which at present is 600GB. But it also eats up all my RAM so my system slows down til the NSTMP file is fully built. I use this as imap with Gmail installed on a PC with a 1TB SSD Today after my pc started slowing again, I started poking around and noticed my main Inbox is massive, 29GB, which there is no chance its that large. All Mail is only 1GB to give perspective This has been going on about a week. I tried repairing my inboxes and other folders, but that does not seem to have helped.