Outlook script to replace empty subjects

CheckEmptySubject.vba

Private Sub CheckEmptySubject()
    Dim fi
    Dim mi As Object
    Dim s As String
    Set fi = Application.GetNamespace("MAPI").GetDefaultFolder(olFolderInbox)
    If fi.Items.Count <> 0 Then
        Set mi = fi.Items.Item(fi.Items.Count)
        If mi.Subject = "" Then
            mi.Subject = "<E-mail without subject by " & mi.SenderName & " on " & CStr(Now) & ">"
            'mi.ConversationTopic
            mi.Save
        End If
    End If
End Sub

Private Sub Application_NewMail()
    CheckEmptySubject
End Sub