A method in a communication network of delivering messages associated with an information exchange service. A message, to be delivered between two entities is interrogated to determining if the data content has already been delivered to the terminating entity. If the data content has not already been delivered to the second entity, the message is transmitted to the second entity unchanged, while the message is modified, so that the modified message comprises a data identifier, identifying the data content, but no data content. The modified message is then transmitted to the terminating entity, and the data identifier is cached together with the associated data content when a successful transmission of the message has been verified. The suggested versioning mechanism enables transmission of messages with a reduced size.