I only send to Listia Verified Addresses, so if its giving you problems you may want to open a ticket - Listia Support is really good about helping with this sort of thing.
Usually I go to the bottom of the page & click on Member Support, then on the Listia Help Center page there's a place where it says Submit a Request. If i can't find the answer to my question in the FAQ's then i'll click to Submit a Request.
It confirms that its a real address, and allows you to be covered by Listia Assurance. You can go to this address to request they verify your address if you haven't already: https://www.listia.com/account/addresses