A Method for transmitting a message from a sender (2) to a set of multiple receivers (4a-4d) over a network comprises sending a multicast message (10) to the set of multiple receivers (4a-4d) and receiving acknowledgement messages (12) from a subset of the receivers (4a, 4b, 4d), each acknowledgement message (12) indicating the receipt of the multicast message (10) by a single receiver. The method further comprises sending a unicast message (14) to a receiver of the set of receivers which is not part of the subset of the receivers (4c).