There are only a few causes of mail going directly 5t6o trash, and I am not aware of any that actually involve Thunderbird (except poorly thought out message filters that is) 1. Anti spam tools both the anti virus program kind and the kind provided by your ISP/Mail provider can see this happening 2. Server side filter that have poor logic trashing mail it is not meant to touch. 3. Third party spam management tools like spam fighter etc that can use your address book. (not your Thunderbird one your empty windows contacts) to drop mail in to trash. So "Brighthouse says Microsoft is having a problem" is really meaningless to me. Are you using a Microsoft mail provider? (hotmail/outlook.com/MSN etc) for them to be blaming Microsoft?