Remove JavaScript validation for the email field in EE3. First example requires WordPress 4.5 or greater. See other code example for sites that have WP 4.4 or lower.

functions.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

function eethree_jquery_validator_custom(){
    wp_add_inline_script( 
        'validation',
        'jQuery(document).ready(function($){
            $(".email").removeClass("required");
            $("label[for=\'email\'] em").hide();
        });'
    );
}
add_action( 'wp_enqueue_scripts', 'eethree_jquery_validator_custom', 50 );

olderwp.php

<?php
//* For sites with WP 4.4 or lower. Doesn't use wp_add_inline_script().
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

function eethree_jquery_validator_custom(){
    if( wp_script_is( 'validation', 'done' ) ) { 
        ?>
        <script>jQuery(document).ready(function($){
            $(".email").removeClass("required");
            $("label[for='email'] em").hide();
        });
        </script>
        <?php
    }
}
add_action( 'wp_print_footer_scripts', 'eethree_jquery_validator_custom', 50 );