To edit an email you have received in Outlook:
1)
Double-click the desired message to open it in its own window.
2)
Select Actions | Edit Message from the Move section in the Message ribbon.
In Outlook 2007:
Select Other Actions | Edit Message from the toolbar.
In Outlook 2003 and earlier:
Select Edit | Edit Message from the menu.
Make all desired changes in the message body and Subject: line.
Press Ctrl-S.