Grouping in a Communication System or Service

A computer readable storage medium comprising computer readable instructions which when run on a computer cause that computer to perform a method for instant messaging comprising:

• receiving a message from a member of a first group addressed to said first group;
• determining all child groups which are subordinate to said parent group;
• determining all users of said first group and said determined child groups;
• and
• routing said message to all determined users.

An instant messaging system comprising:

• one or more messaging servers;
• one or more user terminal devices in communication with said one or more messaging servers;
• a directory storing group information of groups used to route messages to multiple users, wherein said directory includes at least one group which is a member of another group;
• and
• wherein said one or more messaging servers is adapted to route messages received from one of said terminal devices to other terminal devices based on said group information.