Managing personal Outlook.com account settings, security, and privacy
Just for clarification - this is happening to me as well but I suspect I know the reason it happens.
The e-mail that's being attempted to be accessed has been compromised in the past - in fact, it's probably featured in multiple data leaks; the most probable cause for multiple people having this issue within a close interval is that there has been a newer leak of old data or that new organizations got access to old leaked data and are attempting to get access to those accounts.
It's probably going through a list of thousands if not millions of addresses, so it probably tries X ways of getting in for each address for a few days and then moves on.
Either it's a fresh leak from Hotmail or it's some app people would have signed up to in mass amounts lately that have had a leak such as zoom or something