http://msdn.microsoft.com/en-us/libr...ffice.12).aspx
Place this in the ThisOutlookSession module.
Untested
Code:
Public WithEvents myOlInspectors As Outlook.Inspectors
Private Sub Application_Startup()
Set myOlInspectors = Application.Inspectors
End Sub
Private Sub myOlInspectors_NewInspector(ByVal Inspector As outlook.Inspector)
Dim msg as Mailitem
If (Inspector.CurrentItem.Class = olMail) Then
Set msg = Inspector.CurrentItem
If msg.Size = 0 Then
MsgBox "Replace the message box with your code."
End If
End If
Set msg = Nothing
End Sub