Outlook change message reply format (“sent by”, etc.)

When replying or forwarding a message Outlook has the default format:

    -----Original Message-----
From: Someone <someone@someplace.com> 
Sent: Date
To: Me <foo@bar.com>
Subject: Outlook formatting

I wish to customize these fields, e.g. changing From: to Sender:. How can I do this in Outlook?