Staged user chose site's contact email address?

We just dealt with a situation where a spammer with a staged account supplied our site’s contact email. We banned the spammer, then had to unban our site’s contact email once it was sorted out.

Is there any mechanism in Discourse where we can forbid staged users (or anyone registering an account) using the site contact email as their email address? Or does having our contact email on the ban-list not affect us receiving support emails from users?