I use categories to sort emails (and rules to automatically assign
categories to incoming email), and have custom search folders to
display emails from each category.  For those emails that I haven't
assigned a category yet, I have a search folder that looks for emails
with no category.  This works great...unless other people have rules on
outgoing email to assign categories that I don't have.

Unfortunately, I can't create a search folder who's filter is "Category
<> my_category 1 OR my_category2", etc.  So, I want to create a
script-driven rule that first removes all categories on incoming email,
then I can let my other rules run to assign my categories.

I am an absolute Outlook macro beginner, but cobbled together the
following code from samples in this group and other websites...
(this is just test code to see if I can manipulate the categories
correctly)

Sub test2(Item As Outlook.MailItem)
  MsgBox "Mail message arrived: " & Item.Subject
   Item.Categories = "Greg"
   Item.Save

End Sub

I have a rule to run this script first on every incoming email.
However, it doesn't appear to work -  I don't even get the msgBox (a
test line), let along the test category assignment.  Can someone help?

Thanks