Redirect any non-business email addresses to a custom page.

gistfile1.phtml

add_action( 'wp_footer', 'tgm_om_force_specific_email_address', 999 );
function tgm_om_force_specific_email_address() {
	
	?>
	<script type="text/javascript">
		jQuery(document).ready(function($){
			$(document).on('OptinMonsterBeforeOptin', function(e, data){
				// Grab the email address submitted by the user.
				var email = $('#om-' + data.optin).find('input[type="email"]').val();
				
				// Test to ensure it is a proper email. Otherwise, redirect to another page.
				if ( /@yahoo\.com$/.test(email) || /@gmail\.com$/.test(email) || /@hotmail\.com$/.test(email) || /@googlemail\.com$/.test(email) || /@live\.com$/.test(email) || /@aol\.com$/.test(email) || /@outlook\.com$/.test(email) || /@comcast\.net$/.test(email) || /@inbox\.com$/.test(email) || /@hushmail\.com$/.test(email) || /@lycos\.com$/.test(email) || /@zoho\.com$/.test(email) || /@gmx\.com$/.test(email) ) {
				    window[data.optin_js].optin = function(){
					    return window.location.href = 'http://thomasgriffin.io/';
				    };
				}
			});
		});
	</script>
	<?php
	
}