You are the messaging engineer for your company. Your company has offices in Denver and Tokyo.
Each office has two Exchange Server 2007 servers that are configured as shown in the following table.
You notice that all e-mail messages sent between offices are delivered by Server2 and Server4.
You need to ensure that all e-mail messages sent between offices are load balanced between two transport servers in each office.
What should you do?
A.
In each office, install the Edge Transport server role on a new server. Remove the Hub Transport server role
from Server2 and Server4.
B.
Install the Windows Clustering service on all Exchange servers.
C.
In each office, install the Hub Transport server role on a new server. Remove the Hub Transport server role
from Server2 and Server4.
D.
Install the Network Load Balancing service on all Exchange servers.
Explanation:
Each Mailbox server maintains a list of the Hub servers also located in its AD site.
To keep this submission server list up-to-date, the server discovery mechanism repeats every ten minutes.When a message is ready for retrieval from a senders mailbox, the Mail Submission Service notifies one of the Hub servers on this list. If the Mailbox server also runs the Hub role, this same machine it notified first. Otherwise, by default, the Submission Service uses round robin to load balance notification events across all the Hub servers in the local site. If the first Hub server cant be contacted, its marked as inactive and the Submission Service fails over to the next server on the list. This way, each active Hub server processes an equal share of messages.
http://technet.microsoft.com/en-us/library/bb232193.aspx
Load balancing applies to all types of outgoing mail connectors on both Edge and Hub servers — SMTP, Routing Group, Foreign. If multiple source servers from one AD site are configured on such a connector, load balancing is achieved by distributing links across all these servers in a round robin fashion. However, load balancing doesnt take place if the machine relaying the mail is itself configured as a source server for that particular connector. In this case, local server proximity takes precedence over local AD site proximity, and the mail is always routed by this same computer.
http://technet.microsoft.com/en-us/library/bb267003.aspx