Ofcourse you can fake it. If you have control the desktop then you can set it up anyway you like, including with faked mails in outlook.
Just how trivial that is depends on your goal.
But before you try this: Having an email in the 'sent' folder does not mean it has been sent. Even without trickery. It just means that outlook tried to sent it. If it failed to do so (e.g. because you had no working network connection, or the server was flaky) then it still appears in the sent folder.
And even if everything worked as intended at your side that does not mean the recipient received the mail. There is no guarantee on mail. Neither on email or paper-mail. You can test this if you want by posting a 1000 letters to people. In all likelyhood a few will not arrive. Same for email.
(Please do not try this IRL unless you want to be marked as a spammer).
[Edit]: Also see how-to-prove-that-an-email-has-been-sent