-fname Sets  the  name  of  the ``from'' person (i.e., the envelope sender of the mail).  This address may
              also be used in the From: header if that header is missing during initial submission.  The envelope
              sender  address is used as the recipient for delivery status notifications and may also appear in a
              Return-Path: header.  -f should only be used by ``trusted'' users (normally root, daemon, and  net-
              work)  or  if the person you are trying to become is the same as the person you are.  Otherwise, an
              X-Authentication-Warning header will be added to the message.