HP 3000 Manuals

Installing and Configuring HP X.400 Administrator's Guide

How Are Messages Delivered 

A message may be sent from one MTA to another MTA until the message
reaches the recipient's MTA, which then delivers it to the recipient UA.
Each MTA is responsible for the message until the next MTA acknowledges
receipt of the message.  Once receipt has been confirmed, the next MTA is
responsible for the safe storageof the message.  Figure 2-2 shows that
MTA 3 is directly connected to each of the other MTAs, but MTA 5 is
directly connected only to MTA 3.  To send a message to any other MTA,
MTA 5 must use MTA 3 as a relay.


          Figure 2-2.  Message Transfer System 

Each user is associated with one UA. A user can read, create, edit, and
send messages by accessing the MHSthrough the associated UA. Each UA is
associated with one MTA. When a user sends a message to another user, the
user's UA sends the message to its associated MTA. Multiple MTAsmay be
involved in the relaying of the message.  When the message arrives at the
final MTA, it is delivered to the UA of the recipient user.  If a message
is to be delivered to multiple recipients, the message is delivered to
the MTAs which then perform any duplicating 
necessary to deliver the message to each of the recipients.


          Figure 2-3.  MTAs and UAs 

Figure 2-3 shows that an MTA such as MTA 2 does not need to have a UA or
multiple UAsassociated with it.  An MTA with no associated UA will only
be used for relaying.  An MTA such as MTA 3 with associated UAs may or
may not perform relaying.

MPE/iX 5.0 Documentation