original_string: public function setReturnPath($email)
      {
          if ($this->_returnPath === null) {
              $email = $this->_filterEmail($email);
              $this->_returnPath = $email;
              $this->_storeHeader('Return-Path', $email, false);
          } else {
              /**
               * @see Zend_Mail_Exception
               */
              // require_once 'Zend/Mail/Exception.php';
              throw new Zend_Mail_Exception('Return-Path Header set twice');
          }
          return $this;
      }
code: public function setReturnPath($email)
      {
          if ($this->_returnPath === null) {
              $email = $this->_filterEmail($email);
              $this->_returnPath = $email;
              $this->_storeHeader('Return-Path', $email, false);
          } else {
              /**
               * @see Zend_Mail_Exception
               */
              // require_once 'Zend/Mail/Exception.php';
              throw new Zend_Mail_Exception('Return-Path Header set twice');
          }
          return $this;
      }
code_tokens: public function setReturnPath ( $ email ) { if ( $ this -> _returnPath === null ) { $ email = $ this -> _filterEmail ( $ email ) ; $ this -> _returnPath = $ email ; $ this -> _storeHeader ( 'Return-Path' , $ email , false ) ; } else { /**
               * @see Zend_Mail_Exception
               */ // require_once 'Zend/Mail/Exception.php'; throw new Zend_Mail_Exception ( 'Return-Path Header set twice' ) ; } return $ this ; }
docstring: Sets the Return-Path header of the message
  
  @param  string    $email
  @return Zend_Mail Provides fluent interface
  @throws Zend_Mail_Exception if set multiple times
docstring_tokens: Sets the Return - Path header of the message