Your company has Two offices. The relevant portion of the network is configured as shown in the exhibit

Each office contains three Exchange Server 2003 servers. You configure a routing group for each office. You configure a routing group connector between the two routing groups.

The routing group connector is configured to have all the default settings.

Users report that some e-mail messages sent between the two offices are not delivered.

You need to ensure that all messages sent between offices are delivered.

What should you do?

A.
Move all Exchange Server 2003 servers to a single routing group.

B.
Modify the routing group connector to use EX1 and EX4 as bridgehead servers,

C.
Configure the firewalls to allow RPC communication between all Exchange Server 2003 servers,

D.
Create a new SMTP connector between the two routing groups. Add the SMTP virtual servers in each routing group as bridgehead servers