A method of communicating a message from a sender to a recipient in possession of a unique identifier by use of which the recipient can perform a transaction at a transaction terminal includes: receiving the message from the sender, the message including a reference to the unique identifier; storing the message in a computer memory; detecting performance by the recipient of a transaction at the transaction terminal; and transmitting the message from the computer memory in which it is stored to the transaction terminal for display to the recipient incidental to the transaction performed, the message being independent of the transaction performed. Apparatus for communicating a message from a sender to a recipient in possession of a unique identifier by use of which the recipient can perform a transaction at a transaction terminal comprises: a first communication network; a second communication network including a transaction terminal; a computer memory; one or more processors collectively executing a sequence of instructions defining functions of receiving the message over the first communication network; storing the message in the memory; detecting performance by the recipient of a transaction at the transaction terminal; and transmitting the message over the second communication network. The recipient may be selected from a target list of recipients identified with a sponsor, wherein the message includes a reference to the target list.