Using classic Outlook for Windows in business environments
this is the second time I've had this problem after 15 years using outlook. I recently read Microsoft was doing this to encourage users to pay for an upgrade to their outlook account and they fix the junk problem with the upgrade.
Try this: click all the spam in your inbox (in my case all the spam subject started with "Re:....text"). click "Report Phishing or Report Junk". After a few days the junk didn't appear in my inbox.