Idk, I think Microsoft could get away with a lot. Not selling your emails to the highest bidder, that might be a bridge too far, but training an LLM on Outlook emails? Probably. Just have an LLM scan every email to see if its contents are mundane or secret first, and only use the mundane ones. There might be a scandal of some sort, then Microsoft would say sorry (but keep the model), and then everyone would move on because the switching costs are too high.