If you don't want to use a submission service like Litmus (Litmus is the best, BTW) then you're just going to have to run Outlook 2007 to test your email.
It sounds like you want something a little more automatic (though I'm not sure why), but fortunately Outlook is easy to automate using Visual Basic for Applications (VBA).
You can write a VBA tool that runs from the command line to generate an email, load the email up in Outlook, and even capture a screenshot if you wish. (Presumably this is what the Litmus team does on the backend.)
(BTW, do not attempt to use MS Word to test mail; the renderer is similar but subtle differences in page layout can affect the rendering of your email.)