Troubleshoot: Spam delivered to Inbox instead of Junk E-mail folder

On rare occasions you may experience that spam messages are (consistently) delivered to the Inbox folder instead of the Junk E-mail folder even though it is rated at SCL: 9

The graphic below shows the properties of an e-mail rated at SCL: 0 as an example.

If you get mails with SCL level 5-9 in your inbox even though you enabled junk e-mail filtering in Outlook as shown below:

Then open OWA Settings, disable filtering and click save. Then re-enable filtering and save.

Now spam should go to your Junk E-mail Folder…