Hi,
I recommend to use the (Application).ItemSend event.
'ThisOutlookSession
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim msg As String
Dim att As Outlook.Attachment
If TypeOf Item Is Outlook.MailItem Then
If Item.Attachments.Count > 0 Then
msg = "This message contains the following attachments." & vbNewLine & _
"Do you want to send it as it is?" & vbNewLine
For Each att In Item.Attachments
msg = msg & vbNewLine & "* " & att.FileName
Next
If MsgBox(msg, vbQuestion + vbSystemModal + vbYesNo) = vbNo Then Cancel = True
End If
End If
End Sub