That's strange. If I google your subject line "How to Create a UserForm List Box in Outlook" (with quotes) the very first hit is to a page on a help site that has exactly this same title, including exactly the same capitals. That gives the impression that you already knew tbat page. But why then did you ask here?
And just in case you didn't know that page, I told you how to find it.
How to Create a UserForm List Box in Outlook?