The topological relationship of the electronic mail service agents' connection to the server subsystem is simple: it is a star. The centre of the star is the electronic mail service subsystem, and branches are the clients' service agents. While there may be structure within the mail service subsystem, it is hidden to the client. This topology reduces the number of components that are under the operational responsibility of the client to just the electronic mail service agent, and the administrative service agent. It also consolidates the points of failure that could have system-wide effects under one monitoring and operational authority.
As discussed in section 
,
the relationship of the client
to the service provider
makes use of an aggregation strategy,
resulting in
a three-level system.
At the lowest level is the service provider itself,
in the form of a service provider contact point.
The next level is the local electronic mail administrator
and then comes the client.
The affiliation of client to administrator
may be performed by any convenient relationship,
including, but not limited to:
Provision will need to be made for clients that have no initial group affiliation. They will need to be assigned to some administrator, possibly provided by the service provider, and have their status reviewed as other potentially related clients subscribe to the service. If enough related new clients subscribe, a local administrator may be created, leading to the reassignment of the client.
It is important to note that the service provider contact may not be a single person or point. It may be desirable to have a contact point per domain, or per department. This is an issue related to how the service provider organizes, and is beyond the scope of this report.
The relationship of the service provider,
client group and client is illustrated in
figure .
interfacesOverview of Model