I entered an invalid address on my own server into the verifier form and received:

  deliverable: Yes
  valid format: Yes
  disposable: No
  server status: Yes
  role: Yes
  free: No
  email user: nobody
  email domain: zzo38computer.org

I don't know what all of that means, but the address is not valid and you cannot send messages to it.

An interesting result when you put in mailshunt.com