You are a messaging professional. Your company has 60 Microsoft
Exchange Server 2003 computers in 27 offices. A Microsoft Active Directory site and an Exchange
Routing group are configured for each office.

Six of the offices are your companys regional headquarters. In your companys main office and each
regional headquarters, one or more Exchange Server 2003 computers are used as Microsoft Outlook Web
Access (OWA) front-end servers. Users connect to the OWA front-end servers in their own region to
access their mailboxes on the Internet.

Your company plans to upgrade all Exchange Server 2003 computers to Microsoft Exchange Server 2007
computers in the next 12 months. Your company wants to maintain all existing functionality during the
migration.

Your companys messaging administrators create the following upgrade plan:

First, upgrade the main office in the following order:

1. Install Exchange Server 2007 computers as Mailbox servers and Hub Transport servers.
2. Move all mailboxes to the Exchange Server 2007 computers.
3. Replace the OWA servers with Exchange Server 2007 Client Access Servers.

Next, upgrade the regional offices in the same order.

Finally, upgrade the remaining offices in the following order:

1. Install Exchange Server 2007 computers as Mailbox servers, Hub Transport servers, and Client Access
Servers.
2. Move all mailboxes to the Exchange Server 2007 computers.

You need to modify the plan to support the coexistence of Exchange Server 2003 computers and
Exchange Server 2007 computers during the migration. You also need to ensure that all the existing
messaging services are maintained.

What should you do?

A.
In offices without OWA front-end servers, install one or more Exchange Server 2007 Edge Transport
servers.

B.
In offices with OWA front-end servers, replace the OWA front-end servers before moving the Mailbox
servers.

C.
In offices with OWA front-end servers, replace the OWA front-end servers with Exchange Server 2007
Edge Transport servers.

D.
In offices with OWA front-end servers, replace the OWA front-end servers only after all mailboxes in all
offices have been moved.