Well, it's probably the VBScript of the year from me, but here goes;
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
If (InStr(1, Item.Body, "attached", vbTextCompare) > 0 Or InStr(1, Item.Body, "attachment", vbTextCompare) > 0) Then
If Item.Attachments.Count = 0 Then
Application.ActiveInspector.Activate
ans = MsgBox("It looks like you may have forgotten an attachment, would you like to send the e-mail now?", vbYesNo)
If ans = vbNo Then Cancel = True
End If
End If
End Sub
Now, the only thing this script does is scan your mail text and look for attachment-words (in this case, "attached" & "attachment", in my own version I added some Norwegian words as well), and if they exist and there are no files attached, a message box appears, offering to stop the mail from leaving you un-attached.
Thanks to these guys for the code.