HP-UX System Administrator's Guide: Configuration Management

Networking Topographies
Although there are many ways to configure electronic mail for a group of computers
under your control, the following setups are often used:
□ Central Mail Hub
□ Gateway Mail Hub
□ Fully Distributed
Central Mail Hub
A central mail hub (a mail server) receives e-mail for its users and the users on the
client computers that it serves. Users either NFS-mount their incoming mail files to
their local computers (the clients), or log in to the hub to read their mail. Electronic
mail can be sent directly from the client computers.
Advantages: Only one computer needs to be connected to the outside
world, which protects (hides) the local clients from the
•
network outside, giving the appearance that all mail from
the workgroup is coming from a central computer.
• Only one computer needs to run the sendmail daemon
(to “listen” for incoming e-mail).
• Data are centralized (easier to backup and control)
Disadvantages: Users of client machines must NFS-mount their incoming
mail files from the hub (or log in to the hub) in order to
read their mail.
•
• All electronic mail, even between client machines in a local
workgroup, must go through the hub computer. This means
that local mail traffic could be slowed if the hub machine
becomes overloaded; and mail traffic would stop completely
if the hub goes down or becomes disconnected from the
network.
Gateway Mail Hub
A gateway mail hub receives electronic mail for its users and users of client computers
that it serves. The hub forwards mail intended for users of the client computers to those
clients. Users do not NFS-mount their incoming mail files to their local (client)
computers; they send and receive their mail directly from their own machines.
Advantages: Only one computer needs to be connected to the outside
world, which protects (hides) the local clients from the
•
network outside, giving the appearance that all mail from
the workgroup is coming from a central computer.
• Traffic between local machines (within the workgroup)
does not have to travel through the hub computer because
Components of an Electronic Mail System 123