Making Attachment Name the Message Subject

Paste the code into the 'ThisOutlookSession' module and restart Outlook. As soon as you add a new attachment to an email its name will be displayed as the subject of the message.

  How to add macros to Outlook

Private WithEvents Mail As Outlook.MailItem
Private WithEvents Inspectors As Outlook.Inspectors

Private Sub Application_Startup()
  Set Inspectors = Application.Inspectors
End Sub

Private Sub Inspectors_NewInspector(ByVal Inspector As Inspector)
  If TypeOf Inspector.CurrentItem Is Outlook.MailItem Then
    Set Mail = Inspector.CurrentItem
  End If
End Sub

Private Sub Mail_AttachmentAdd(ByVal Attachment As Attachment)
  Mail.Subject = Attachment.DisplayName
End Sub