function is_email( $email, $deprecated = false ) {
  if ( ! empty( $deprecated ) ) {
    _deprecated_argument( is_email, '3.0.0' );
  }

  // Test for the minimum length the email can be.
  if ( strlen( $email ) < 6 ) {
    
/**
 * Filters whether an email address is valid.
 *
 * This filter is evaluated under several different contexts, such as 'email_too_short',
 * 'email_no_at', 'local_invalid_chars', 'domain_period_sequence', 'domain_period_limits',
 * 'domain_no_periods', 'sub_hyphen_limits', 'sub_invalid_chars', or no specific context.
 *
 * @since 2.8.0
 *
 * @param string|false $is_email The email address if successfully passed the is_email() checks, false otherwise.
 * @param string       $email    The email address being checked.
 * @param string       $context  Context under which the email was tested.
 */
    return apply_filters( 'is_email', false, $email, 'email_too_short' );
  }

  // Test for an @ character after the first position.
  if ( strpos( $email, '@', 1 ) === false ) {
    
/** This filter is documented in wp-includes/formatting.php */
    return apply_filters( 'is_email', false, $email, 'email_no_at' );
  }

  // Split out the local and domain parts.
  list( $local, $domain ) = explode( '@', $email, 2 );

  /*
	 * LOCAL PART
	 * Test for invalid characters.
	 */
  if ( ! preg_match( '/^[a-zA-Z0-9!#$%&\'*+\/=?^_`{|}~\.-]+$/', $local ) ) {
    
/** This filter is documented in wp-includes/formatting.php */
    return apply_filters( 'is_email', false, $email, 'local_invalid_chars' );
  }

  /*
	 * DOMAIN PART
	 * Test for sequences of periods.
	 */
  if ( preg_match( '/\.{2,}/', $domain ) ) {
    
/** This filter is documented in wp-includes/formatting.php */
    return apply_filters( 'is_email', false, $email, 'domain_period_sequence' );
  }

  // Test for leading and trailing periods and whitespace.
  if ( trim( $domain, " \t\n\r\0\x0B." ) !== $domain ) {
    
/** This filter is documented in wp-includes/formatting.php */
    return apply_filters( 'is_email', false, $email, 'domain_period_limits' );
  }

  // Split the domain into subs.
  $subs = explode( '.', $domain );

  // Assume the domain will have at least two subs.
  if ( 2 > count( $subs ) ) {
    
/** This filter is documented in wp-includes/formatting.php */
    return apply_filters( 'is_email', false, $email, 'domain_no_periods' );
  }

  // Loop through each sub.
  foreach ( $subs as $sub ) {
    // Test for leading and trailing hyphens and whitespace.
    if ( trim( $sub, " \t\n\r\0\x0B-" ) !== $sub ) {
      
/** This filter is documented in wp-includes/formatting.php */
      return apply_filters( 'is_email', false, $email, 'sub_hyphen_limits' );
    }

    // Test for invalid characters.
    if ( ! preg_match( '/^[a-z0-9-]+$/i', $sub ) ) {
      
/** This filter is documented in wp-includes/formatting.php */
      return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
    }
  }

  // Congratulations, your email made it!
  
/** This filter is documented in wp-includes/formatting.php */
  return apply_filters( 'is_email', $email, $email, null );
}