The Below Code WORKS for Woocommerce Registration

// Allow Registration Only from .com.au or .au email addresses

add_action(‘woocommerce_register_post’,’is_valid_registration_email_domain’, 10, 3 );
function is_valid_registration_email_domain( $username, $email, $validation_errors ){
$valid_email_domains = array( ‘.com.au’, ‘.au’ ); // Allowed domains
$valid = false; // sets default validation to false
foreach( $valid_email_domains as $d ){
$d_length = strlen( $d );
$current_email_domain = strtolower( substr( $email, -($d_length), $d_length));
if( $current_email_domain == strtolower($d) ){
$valid = true;
break;
}
}

// Return error message for invalid domains
if( ! $valid ){
$error_text = __( “<strong>ERROR</strong>: Registration is only allowed from selected approved domains. If you think you are seeing this in error, please contact the system administrator.”, “woocommerce” );
$validation_errors->add( ‘domain_whitelist_error’, $error_text );
}
}