Yeah, we have blocked disposable email services.
Whatever you do, DON’T block Gmail. That’s used legitimately by millions of people every day. I’ve had plenty of sales in the past from people using that as their primary email account, and in an old job I had, public customers had to have an email account with us and yep, a heck of a lot of them used Gmail to sign up.
Don’t forget that Gmail requires new users to provide a cell (mobile) phone number to sign up now, so Gmail can’t really be considered disposable at all, especially in the manner that places like Mailinator are.