public function addSender( $senderName, $senderEmail ) {
        if( empty( $senderName ) || empty( $senderEmail ) ) {
            return $this->handleError( 'Empty sender name or email' );
        }

        $data = array(
            'email' => $senderEmail,
            'name'  => $senderName
        );

        $requestResult = $this->sendRequest( 'senders', 'POST', $data );

        return $this->handleResult( $requestResult );
    }