by Syed Muhammad Usman on WordPress.org
An add-on plugin for Everest Forms that allows the Blacklisting of specific field's value and emails and email domains by form.

Email Blacklist Add-on for Everest Forms was built to help block submissions from users with generic or competitors email addresses or email domains or specific field value. Prevent the blacklisted user’s form for being saved.
This plugin allows site admins to save a list of field value, emails, domains.
This plugin works by blocking either individual email addresses (exmple: someone@somewhere.domain), email address domains (exmple: google.com).
Navigate to Everest Forms > Emails Blacklist here you can block by email addresses or field or domain, and Save.