Hi Woody,
Sorry for the inconvenience.
According to the discussion (http://answers.microsoft.com/en-us/mac/forum/macoffice2011-macoutlook/how-do-i-request-read-receipt-in-outlook-2011-for/082cfbaf-359b-490a-a6d3-7ef023a15739) in our Outlook for Mac forum, the feature is not supported in Outlook for Mac currently.
Given the information above, since the feature is not available for now, I suggest you submit feedback to our products team about the feature via: Feedback. We are striving to capture any and all product improvements/issues so as to ensure that we are continuously developing/improving Microsoft products to meet our customers' needs. That is exactly why feedback such as yours is always highly valued, thanks for your time.