A network node of a communications system that routes short messages in a home network of a mobile station provides a service where one or more functions are invoked in response to receiving a request to forward a short message addressed to the mobile station. When the network node receives a request to forward a short message it determines a type of transmission of the received short message, where the type of transmission indicates whether or not a request for forwarding the same short message has been previously received in the network node. The network node then invokes functions of the service according to the determined type of transmission.