/**
  * Assigne l'adresse email de notification de paiement
  *
  * @param string $email_ack
  * @return boolean
  */
 public function setEmailAck($email_ack)
 {
     if ($this->_locked) {
         return false;
     }
     $email_ack = trim($email_ack);
     if (strlen($email_ack) > HIPAY_MAPI_MAX_ACKMAIL_LENGTH || !HIPAY_MAPI_UTILS::checkemail($email_ack) && $email_ack != '') {
         return false;
     }
     $this->email_ack = $email_ack;
     return true;
 }