If Microsoft makes an update to their mail programs or if I move a folder in mail program, my e-mails are downloading again when they have already been downloaded. Activity manager on Thunderbird says it is synchronizing my largest folder. I thought it was already downloaded. The headers have been downloaded. Do I have something on Thunderbird set wrong? Or is Microsoft and Hotmail causing this problem? This is costing me internet allowance and money. I hope someone knows how to fix this.