Hub Transport Server role under the hood
Exchange 2007 Hub Transport Server role is evolved version of bridgehead server in previous version of Exchange. At least one Hub Transport Server is required per Active Directory Site where it contains Mailbox server. It provides Mail flow, routing, categorization, delivery for Exchange organization. When configured, it can also provide Anti-spam service. As the name state Hub Transport Server is the hub for mail flow in Exchange organization. This means every message in the organization must go through Hub Transport Server. This allows Hub Transport Server to provide new features such as journaling, transport rules and disclaimers.
Hub Transport server uses AD site topology to determine the routing path. This means, it is very important to associate subnets to proper sites. Exchange 2007 organization will not perform without a properly designed site and subnet infrastructure. Below diagram illustrate how Exchange 2007 uses AD site topology to route messages. When User A sends a message to User B and User C, It routes the message to Site1 > Site2 > Site3. Then, from there Hub Transport copy the message and send it Site4 and Site 5.
In reality Exchange 2007 Hub Transport Server can be single point of failure as email will not flow when Hub Transport Server is down. I encourage IT administrators to deploy at least two Hub Transport Servers per site. Also, remember that you can install Hub Transport Servers role together with Mailbox server role or Client Access role.
Email Policy Compliance features
Hub Transport server provides Email Policy compliance features to organizations. This allows IT administrators to control, restrict the content of email messages in the organization. Microsoft likes to call this an ethical firewall. I call it Outlook rules for the entire organization. This “ethical firewall”, allows IT administrators to:
- Reject messages by subject, content or attachment name
- Reject messages between certain personals
- Restrict messages by attachment type or size
- Archive messages for compliance purposes
- Add disclaimers to email messages and a lot more..
Exchange 2007 Transport Rules
Transport Rules allow IT administrators to control message flow and message content in Exchange organization as mentioned earlier. These transport rules are stored in Active Directory. Hub Transport rule agent use these rules to enforce compliance. Transport rules can be created from Exchange Management Console > Organization > Hub Transport
SMTP Receive Connector
SMTP Receive Connector listens on port 25 to accept SMTP connections. This is very similar to SMTP Virtual Server concept in Exchange 2000/2003. SMTP Receive Connector is server specific and exists on every Hub Transport server. You need to configure the SMTP Receive Connector when third party software needs to use it a relay server.
Exchange 2007 SMTP Receive Connector
Exchange 2003 SMTP Virtual Server
Install Hub Transport server role
Installation of Install Hub Transport server role is pretty straight forward. Choose custom installation during the install and check the Hub Transport role. If the prerequisites are not meet, the installer will inform you with the list.
How to configure SMTP Send connectors
Once Hub Transport role is installed, first thing we want is to configure SMTP Send connectors. By default, you will receive inbound mail but it won’t send without SMTP Send connector. Below is different type of SMTP Send connectors:
Different type of SMTP Send connectors
Internal
Internal SMTP Send connector is used route email to Hub Transport servers in different site and Edge Transport servers.
Internet
This type of SMTP Connector is used to send email to the internet. This connector will be configured to use DNS MX records to route e-mail.
Custom
Custom send connector can forward mail to third-party email servers
How to create SMTP Send connector
- Open Exchange Management Console
- Browse to “Organization Configuration” > “Hub Transport”
- Select New Send Connector
- Enter the name
- Choose connector type
- Enter SMTP Address space
- Click Next three times
- Click New
- Click Finish