WP Allow User Registration from specific domain emails

code.php

add_filter( 'pre_user_email', function( $email ) {
	$allowed_domains = array(
		'example.com',
		'yoursite.com',
	);
	
	if ( ! is_email( $email ) ) {
		return $email;
	}

	$user_domain = explode( '@', $email )[1];
	
	if ( ! in_array( $user_domain, $allowed_domains ) ) {
		wp_send_json_error( array(
			'code'		=> 'invalid_domain',
			'message'	=> 'Sorry, you are not allowed to register.',
		) );
	}
	
	return $email;
}, 10 );