1. A messaging system comprising a messaging engine for operating under user instructions to generate and transmit messages addressed to recipient contacts; characterised in that the system comprises a server comprising: a client interface ( 4 ) comprising means for allowing access by a plurality of users of registered clients; a client manager ( 2 ) comprising means for maintaining a database of registered clients; a content manager ( 25 ) comprising means for receiving content items uploaded from users and for storing said content in a content database ( 26, 27, 29 ); means in the content manager ( 25 ) for selecting content items for a message; means in the messaging engine ( 21 ) for generating and sending a message with links to selected content items in the content database; a response management function ( 22 ) comprising means for monitoring a response from a recipient contact using said links; a build function ( 20 ) comprising means for building content for the responding recipient contact according to the links used by said contact to respond; and means in the response management function ( 23 ) for sending the built content to the responding recipient contact.