I am sorry that you had to wait 5 days for an answer to your questions in your 1st post. I do not use Outlook but I did a little research to see what I could find.
From my understanding McAfee has been the Security program of choice by Microsoft that scans your POP3 traffic before it arrives to Outlook. If it wasn't there before it could be due to an update or added security feature to the McAfee program used by Microsoft. Since I don't use Outlook I can't verify this for you. There is no harm having it there though. It is just an extra precautionary measure that for some could be construed as a hindrance.
The folder may reappear again. If it does, just go to the McAfee Anti-Spam folder, open it and Right click
on the e-mails you know are legitimate and you should be presented with an option to Add Friend
and it should from then on place those e-mails into your InBox. If they end up in the Outlook Junk E-Mail folder you may have to do the same till they end up in your InBox in Outlook.
As I stated above McAfee is a chosen program by Microsoft to scan incoming Outlook mail just as Norton is the chosen program for my Yahoo incoming mail though I do not
have Norton installed on my computer as you do not have McAfee installed on your computer.
If you have anymore concerns or questions please don't hesitate to ask.