The plugin User - Email Check has now been published in the Joomla Extensions Directory (JED). It validates the email domain, the part that comes after the @ sign, by looking it up from the Domain Name System (DNS).
The plugin checks the email field in the user data, when it is entered into the registration form or the profile form by the frontend user or edited by the administrator through the backend of the website.
More information and links to the support forum available from https://extensions.talikka.com.