There is provided a messaging system comprising at least one distributed front-end messaging system and a centralized data store associated with said at least one distributed front-end messaging system, in which system the centralized data store includes means for storing data associated with users of the at least one distributed front-end messaging system, the at least one distributed front-end messaging system further including a respective at least one cache means for storing at least a portion of the centralized data associated with users of said at least one distributed front-end messaging system such that at least one messaging function can be provided to users of said at least one distributed front-end messaging system in dependence on the data stored in said cache means. A centralized messaging system provides access to all stored data associated for all users associated with at least one distributed front-end messaging system.