

The Replies and Forwards section is about halfway down. To change the reply format in Outlook 2010 or newer: Go to File, Options, Mail. Note that this is not necessary in Outlook 2010 as you can use the Forward as attachment command on the right click Context menu or More command in the ribbon. If you only need to forward one message as an attachment, delete the second message.

If you need to forward a message as an attachment you can do it "on the fly" by selecting more than one message and hitting Forward. Stick with include original message or prefix each line formats. However, because most users prefer to have the last message quoted in the reply and many are annoyed by unnecessary attachments, I don't recommend using either reply format. While original and prefix original are the most commonly used formats, the "Do not include original message" and "Attach original message" reply formats (1 and 2 in the screenshot) will use your stationery because Outlook begins with a blank message.
