Exchange Server 2010 : Configuring Transport Servers - Hub Transport Servers (part 1)

1. Hub Transport Servers

Hub Transport servers process all messages that transit an Exchange Server 2010 organization. Hub Transport servers deliver internal or externally sourced messages to user mailboxes and forward messages bound for hosts on the Internet to Edge Transport servers. A component on the Hub Transport server, called the categorizer, determines what to do with each message based on recipient information in the message header. The categorizer expands distribution lists, identifies alternative recipients, and processes recipient forwarding addresses. The categorizer also applies policies, routes messages, and converts content. Hub Transport servers receive messages through the SMTP protocol from other transport servers or by picking them up from a sender’s Outbox using the store driver. Hub Transport servers use send and receive connectors to transmit messages to other locations.

If your organization does not use an Edge Transport server, you can configure the Hub Transport server to relay messages directly to hosts on the Internet, such as a third-party smart host. It is also possible to enable the Edge Transport server anti-spam agents on the Hub Transport server role as well as configure a Hub Transport server to scan messages for malicious content by deploying antivirus protection.

You must deploy a Hub Transport server in each Active Directory site that hosts an Exchange server with the Mailbox server role. You can install the Hub Transport role on servers that already host the Client Access and Mailbox server roles. You can deploy more than one Hub Transport server in each site to provide redundancy without having to configure Domain Name System (DNS) round-robin or network load balancing.

An Exchange organization can accept messages for a particular email domain only if that mail domain is set up as an accepted domain. Accepted domains are also domains for which Exchange is able to send email. For example, if your organization needs to send and accept email for the Contoso.com and Fabrikam.com domains, you need to configure both of these domains as accepted domains. By default, the domain name associated with the forest in which you install Exchange is the default accepted domain for your Exchange organization.

When you configure an accepted domain, you need to specify whether the accepted domain will be authoritative, an internal relay domain, or an external relay domain. Figure 1, the first page of the New Accepted Domain Wizard, displays this choice. The differences between each of these types of accepted domain is as follows:

• Authoritative Domains Accepted domains for which the Exchange organization accepts and stores email messages from external locations. For example, at Contoso, Contoso.com is an authoritative domain, as Contoso.com transport servers deliver messages addressed to Contoso.com recipients to mailboxes hosted on Contoso.com mailbox servers. The default authoritative domain for an organization is the fully qualified domain name of the forest root domain.

• Internal Relay Domains Accepted domains for which the Exchange organization will accept email messages from an external location but forwards them to another mail system located on the internal network. For example, a subsidiary company of Contoso is running a third-party mail system on the internal network. The domain related to this mail system is configured as an accepted domain, but Hub Transport servers route messages directed to recipients at this domain to those internal mail servers rather than delivering the messages to Exchange mailbox servers. You can also use internal relay domains when an organization has more than one Active Directory forest or when recipients in a single email domain are spread between Exchange and a third-party email system. To function properly, internal relay domains require that you configure a send connector to that domain on your organization’s Hub Transport servers.

• External Relay Domains An accepted domain for which the Exchange organization will accept email messages from external locations but does not process them locally and forwards these incoming messages to an external mail server. For example, Contoso.com transport servers might accept messages to recipients with email addresses associated with the domain proseware.com domain, but these transport servers automatically route these messages to a mail server that exists outside the organization’s internal or perimeter network. To function properly, external relay domains require that you configure a send connector to the external domain on your organization’s Edge Transport servers.

You can create a new accepted domain by clicking on New Accepted Domain in the Actions pane when the Organization Configuration\Hub Transport node is selected in Exchange Management Console (EMC). Creating an accepted domain involves specifying the domain name and a label for the name, choosing between the domain being an authoritative, internal, or external relay domain.

You can use one of the following Exchange Management Shell (EMS) cmdlets to manipulate accepted domains:

• New-AcceptedDomain This cmdlet is used to create new accepted domains. Use the DomainType parameter to specify whether the domain will function as an authoritative, external relay, or internal relay domain.

• Get-AcceptedDomain This cmdlet can be used to list the properties of existing accepted domains.

• Set-AcceptedDomain This cmdlet allows you to modify the properties of an existing accepted domain.

• Remove-AcceptedDomain This cmdlet allows you to remove an existing accepted domain.
  

Remote domains allow you to control the types of messages and message formats sent from users in your organization to a specific external domain. When you install Exchange, a default remote domain is created that has the label represented by an asterisk (*). This default remote domain is responsible for the settings applied to all outgoing messages except those configured for specific remote domains. You can edit the properties of a remote domain or create new remote domains through the Organization Configuration\Hub Transport node in the EMC.

You create a new remote domain by clicking on New Remote Domain when the Organization Management\Hub Transport server node is selected from within the EMC and then clicking on New Remote Domain in the Actions pane. When you create a new remote domain, you need to provide a label and the domain name and specify whether all subdomains of that domain will be included. You configure items such as MIME character sets and out-of-office message settings after you create the remote domain by editing the properties of the remote domain.

By configuring a remote domain, you can configure whether specific external domains receive out-of-office messages from recipients in your organization, as shown in Figure 2. For example, you may have configured the default remote domain so that no out-of-office messages are sent to external recipients but decide to configure a special remote domain for a partner so that he or she receives out-of-office notifications.

Remote domain message format options allow you to configure whether automatic replies, automatic forward, delivery reports, and the sender’s name are forwarded to a remote domain. It also allows you to specify whether Exchange rich text format is used and which MIME and non-MIME character set is used. Figure 3 shows the cohovineyard.com remote domain configured to use the Cyrillic (ISO) character set. You would configure a specific remote domain message format when the default is appropriate. For example, there are four separate Cyrillic MIME character sets, and when messages are sent using the wrong character set, messages are not formatted correctly for their intended recipient. In general, you will need to discuss which character set is appropriate for a specific remote domain with a representative of the recipients in that domain.

Four EMS cmdlets allow you to configure and manage remote domains:

• New-RemoteDomain Create a new remote domain entry

• Set-RemoteDomain Modify an existing remote domain entry

• Get-RemoteDomain View the properties of an existing remote domain

• Remove-RemoteDomain Remove an existing remote domain entry