SetSubject
The SetSubject function sets the subject of the
mail.
Syntax
Important: This feature is deprecated, its use is
discouraged although not prohibited.
CALL ui.Interface.frontCall("WinMail","SetSubject",
  [ id, subject ], [ result ] )
- id is the message identifier.
 - subject is the string text containing the subject of the mail.
 - result is the status of the function.