Just go to
www.vrbo.com, click on Members Area, and log in with your User ID and password. (You can get your password by going to
http://vrbo.com/admin/RequestId.asp). Choose to edit your listing, (find your listing number in the middle of the Administration page, and click on the "Edit" button to the right).
Once logged in, scroll down the page, until you see your email address. To the right of that information, you will see a button that says "Advanced option". Click on that button, and you can enter the other email address. Then, when you are finished, click "Next" at the bottom of the page to save your changes. Then, click on "Review" to see your ad on the website. (This particular change will not be displayed, since we do not publish email addresses on the listings.)
You can test the email link by going to your listing online: www.vrbo.com/xxx (your property id). Click on the "Click to send email" button, and then sending a "test" inquiry. Click "Send email now" at the bottom of the form. It should then be directed to the "override" email address that you entered on your listing.