A messaging system comprising: computer storage holding messaging accounts for users of the messaging system, each comprising a user identifier of a first type; an account manager for managing the messaging accounts; a group manager configured to grant participant users access to messaging groups by creating, in the computer storage, associations between the messaging groups and the messaging accounts of the participant users; a group messaging service configured for use in transmitting and receiving messages, in each of the plurality of messaging groups, between the participant users granted access to that messaging group, using the user identifiers of the first type in their messaging accounts.