Deploying Disaster Recovery for Exchange 2010 – Part2

-Authored by Achinta Chatterjee (link to Linkedin Profile)

Introduction

This document is a continuation of the previous article for setting up DR for Exchange 2010. In the previous article we detailed how Client Connections to the Exchange server works both on Primary and DR site. In this article we will begin with the mail routing planning and considerations we need to do for Exchange 2010 for our Disaster Recovery setup.

Disaster Recovery Planning & Considerations

i. Mail Routing

To setup Mail Routing you need to consider the following components:-

a. Exchange Internal Email Routing

b. Primary and DR Site Incoming and Outgoing email Routing

c. Internet Email Routing

a. Exchange Internal Email Routing

For mail routing between Exchange users , nothing has to be separately configured. Even if your users are in Primary and DR site they will be able to send /receive emails among themselves as the RPCClientAccessserver determines what is their Array and then routes the email to the respective databases.

b. Primary and DR Site Incoming and Outgoing email Routing

What we will consider here is Sending and Receiving of external SMTP Internet email routing. Four sections will be discussed here. Primary and DR Site Incoming and Outgoing emails.

Primary Site Incoming Emails

For external emails to be accepted by Exchange servers we need to create Accepted Domains and Receive Connectors.

Accepted Domains. They can be created in EMC under Organization Configuration> Hub Transport

Accepted domains need to be created to tell Exchange the email domains it hosts. Typically thee domain names would be the email address you give to your company for eg. Mycompanyname.com

Receive connectors. They need to be created to tell Exchange from which servers Exchange can receive emails and with what kind of authentication. They can be created in EMC under Server Configuration > Hub Transport. The figure below shows the receive connector that tells exchange from the server under “Receive mail from remote servers that have these IP addresses”. Typically these servers will be your Incoming Internet Mail Relay Servers, that receive Internet Emails. Note they are created under the primary site CAS servers (CAS1/CAS2).

Primary Site Outgoing Emails

Send Connector. For Primary Site Outgoing emails we need to create a Send Connector. In EMC go to Organization Configuration > Hub Transport> Send Connector.

We create a single Send Connector give it an address “*” so that it can send all Outgoing emails from through this connector.

Note we should give this Send Connector a cost of 1.

The Network tab contains the Primary Outgoing Internet Mail Relay Servers under Route Mail through the following Smart host.

The Source Servers contains the CAS/HUB server for which the Send Connector is created. This means emails generating from these servers (which contain the primary CAS server array too) will be directed through this Send Connector.

DR Site Incoming Emails

For external emails to be accepted by DR Exchange servers we need Accepted Domains and Receive Connectors in the DR site as well.

But Accepted Domains don’t need to be created a second time for DR as they are not server specific. They are all kept under the Active Directory configuration and are valid for both Primary and DRsite.

However we need to create Receive Connector for the DR site. This because we have a separate set of Incoming SMTP Internet Relay servers.

However take note we need to create the Receive Connectors under the DR CAS server as shown below.

The field “Receive mail from remote servers that have these IP addresses” should be the of Incoming SMTP Internet Relay servers.

DR Site Outgoing Emails

Send Connector. For DR Site Outgoing emails we need to create a Send Connector. Although this connector is created now, this will be not be used and will be kept as a preparation for DR.

In EMC go to Organization Configuration > Hub Transport> Send Connector.

We will create a single Send Connector give it an address “*” so that it can send all Outgoing emails from through this connector. However we should give this Send Connector a cost more than 1 say 100, as shown below.

The reason why this is done is because we don’t want all emails to go through the DR site during normal conditions. This Send connector will be activated during actual DR.

The Network tab of the Send Connector contains the DR Outgoing Internet Mail Relay Servers under Route Mail through the following Smart host.

The Source Servers contains the CAS/HUB server for which the Send Connector is created. This means emails generating from these servers (which contain the DR CAS server) will be directed through this Send Connector.

c. Internet Email Routing

Now that we have completed with Mail Routing configuration on Exchange Servers, we will briefly go through how the Internet Mail routing should be setup in accordance with DR strategy.

If you are hosting emails for a domain for you must have a MX record in the internet DNS that is pointing to you Incoming Internet SMTP Mail Relay Server.

Generally organizations will have 2 or more Incoming SMTP servers due to redundancy. The way to set this is to configure the MX records to have Priority. So if you have 4 Incoming mail servers 2 in Primary site and 2 in DR site you give higher priority to your servers on the Primary site and lower to the one’s on your DR site. The Priority is also known in DNS terms as Preference. As you can see in the figure below the MX Preference for the DR SMTP server is the least.

This configuration actually makes the DR Strategy for Internet Mail Routing. When your Primary site is down due to a calamity emails automatically starts to route to the lower preference Intenet SMTP Mail Relay servers ie. the DR Servers. This configuration makes it a robust site resilient strategy for any email loss due to a calamity.