When I mailed mine today, the guy at the counter put actual stamps (4.95 worth) on the envelope to be returned to me. I had mentioned to him about the expiration factor of metered mail which is what is used on front envelope and he used actual stamps. And he seemed to know what he was doing so I didn't question him - in fact, he's the only one I like to work with at our post office, but it's a long story....