The Ticket wrote:

I do not know what an on-access scanner is or how to tell if it is
running.

It's the background process of your antivirus scanner. You can usually tell
it's running because it will display an icon in the notification area of the
Taskbar.

Is it a feature of Outlook?

No, it's a feature of the antivirus program you use.

If so, where do I access its settings?

You'll have to read the help in your AV program for that.
--
Brian Tillman [MVP-Outlook]