Using TB 115.15. When I move a large number of messages (200 or so) to a sub folder the move goes fast until it gets toward the end, then it locks up until it finishes a few minutes later. When I tried to move over one thousand messages at one time, I let it run overnight, some messages moved, some only moved a date header of some earlier time (all the same time) and all messages were left intact in the original directory. After moving the messages a few at a time, I had to manually delete the duplicate messages in the sub folder. What is the maximum number of messages Thunderbird will move at one time.