Block submissions from specific email addresses?

We’re having trouble with spam submissions coming in repeatedly. They come in bunches, all submitted from “yahoo@yahoo.com.”

Without setting up Akismet, is there a way to just block submissions from certain email addresses? Like a way that we could tell CF7 to automatically ignore a submission if it comes from that address?

We don’t have widespread problems with spam, it seems like it’s just this one bot (even though we have recaptcha on).

Any help or suggestions would be appreciated.