问题：

[单选]

Your company has a domain controller named Server1 that runs Windows Server 2008 R2 and the DNS server role. A server named Server2 runs Windows Server 2003 and Microsoft Exchange Server 2007. The company wants to deploy a new Exchange server named Server3 to receive all inbound e-mail traffic. You need to configure DNS to direct incoming e-mail traffic to the Exchange servers. You also need to ensure that higher priority is given to Server3. 
What should you do？（）

A . Set the priority value of the Server2 Mail Exchanger (MX) record to 20. Create a new Mail Exchanger (MX) record for Server3. Set the priority value to 5.
B . Set the priority value of the Server2 Mail Exchanger (MX) record to 5. Create a new Mail Exchanger (MX) record for Server3. Set the priority value to 20.
C . Create a new Service Location (SRV) record in the domain for Server3. Set the port number value to 25. Configure the priority setting to 20.
D . Create a new Service Location (SRV) record in the domain for Server3. Set the port number value to 110. Configure the priority setting to 5.