I usually use mailinator.com for this purpose. In the past I found other similar services through Google search, but certainly didn't find yours. Probably working on your website SEO will increase your organic sign-ups. One thing I love about Mailinator is that all inboxes are public, this completely removes the overhead of creating a new email even in a disposable email service like yours. So probably something you may check for your product. Congrats for the achievement!