code: public function smtp(array $params)
      {
          //validate the user params
          if (!array_key_exists('username', $params)) {
              throw new Exception('We need a username');
          }
  
          if (!array_key_exists('password', $params)) {
              throw new Exception('We need a password');
          }
  
          $this->smtp = $params;
          $this->auth = true;
  
          return $this;
      }
docs: Overwrite the baka SMTP connection for this current email
  
  @param  array  $smtp
  @return this