Why is some junk mail appearing in my inbox when my Outlook account is set to Exclusive?

My Outlook has been set to Exclusive for many months.  Just this week, I have been receiving junk mail in my regular inbox.  The e-mail messages are NOT from senders in my contacts list.  I am having to individually select each of those messages and move them to my junk folder.  From the junk folder, I am having to individually select them again and then click on "Sweep" in the menu bar and then select "Block from" on the drop down menu.  This process is very time consuming.  It would be much simpler if the Exclusive setting actually worked as designed (and, as I might say had been working properly for many months).  What is going on?  Why, all of a sudden, is some junk mail now coming to my regular inbox rather than to the junk folder where it is supposed to be going?