"Is your point that, for example, Office 365 should know it when the email header says that a message comes from an Office 365 email server, while in fact it doesn't?"
My point is that a user such as Maintenace Care<firstname.lastname@example.org> (other MS domains are availabe) can send a message with a title such as YOUR HOTMAIL WILL EXPIRE SOME DAYS TIME to a Hotmail (other MS domains are available) user and it's not picked up by their spam filters even if, as is likely, such messages are sent in bulk. That particular one, a couple of weeks ago, carried a docx attachment; yes, I'm really going to open that, aren't I? Then there's the ever faithful "Account Team" who sent not one but two "De activation in progress" emails 5 minutes apart a week or so earlier than that.
This sort of spam is old enough to buy its own drinks
Sometimes, for weeks at a time, they seem able to trap such crap into the spam folder then they have a spate of letting them through.