Please have a look at my post in this thread https://answers.microsoft.com/en-us/outlook_com/forum/all/how-do-i-stop-thousands-of-spam-emails-from-going/144816b1-0923-4556-b42d-bfa1e8062384?page=2 (last one on the page).
It involves creating three simple rules that are clarified by screenshots.
I work at Microsoft and until now, even I haven't been able to get an answer as to why there's so much spam coming into Outlook.com/Hotmail.com. Something is broken but I just don't have the connections internally to speak to the right people to find out what (and I'm in the org unit that does support).
However - I setup what Sendak932 has posted, creating the 3 rules with the screen shots on that link provided. And I can 100% confirm this has reduced the spam considerably. In fact, since this morning (about 6hrs ago) since I enabled these rules - not 1 single spam has come through to my inbox, but there are 63 now in junk mail.
Sendak932 - I thank you!