public function setMail($mail)
    {
        if (!$this->validMail($mail)) {
            return false;
        }

        if ($this->setMailStatement === null) {
            $this->setMailStatement = $this->connection->prepare("UPDATE User SET mail = ? WHERE username = ?");
            $this->setMailStatement->bindParam(1, $this->mail);
            $this->setMailStatement->bindParam(2, $this->username);
        }
        $this->mail = $mail;
        $this->setMailStatement->execute();
        return true;
    }