Target Skills:

Ability to describe the role of Messaging Hubs.

 
     

Dedicated Message Transfer Agents

You can increase messaging performance and share the load by dedicating messaging servers that only transfer messages to where they need to go, and do not have to manage user messaging folders and retrievals of  messages.  These servers are acting only as Message Transfer Agents (MTA's).  These types of servers are typically called Hubs.
 

Inbound Messaging Hub

Accepts incoming messages from the Internet Relay across the firewall.  It does an LDAP query to find out where to send the message, then sends it off to the appropriate server.

Outbound Messaging Hub

Accepts outgoing messages from clients.  It does an LDAP query to find out where to send the message, then sends it off to the appropriate server or out across the firewall to the Internet.  This offloads the MTA work from the messaging servers that are used by users to retrieve their messages.
 

Two Hubs or One?

Often, both the inbound and outbound hubs are combined as a single In/Out SMTP Relay Hub. The decision to do so involves sizing of the messaging system, with the focus on inbound and outbound message traffic characteristics of the overall architecture. 
 
 
 
 
     

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