How To: Delay Emails In Outlook
There are plenty of good reasons to want an email to go out at a different hour than when you wrote it (the most obvious: to fake what hours you do work during). Lifehacker has the instructions for older versions of Outlook.
To do the same thing in Outlook 2007, after writing an email but before clicking Send, click the Options tab in the Ribbon, then click Delay Delivery in the More Options group on the right side. After that, the options are pre-selected for you, usually timing the delivery for the close of business today. Change the date and time to suit your needs, click Close, and enjoy your tomfoolery.
Now, how to I modify email headers to make an email look like I sent it earlier?
Visit the InsideGoogle blog.