We discuss this
further in Chapter 11 .
Most Exchange Administrators do not have permissions to administer the Active Directory Sites and
may not have control over the path that an email could traverse in a large Active Directory site. Two
things can be done in this situation. An administrator may choose to specify a Hub site using
the Set-ADSite cmdlet. This forces all mail flow in that path through the Hub Transport servers in
Chapter 7: Confi guring the Hub Transport Role
213
the designated Hub site before they are routed to their final destination. Something else available to an
Exchange administrator is the ability to introduce an Exchange - aware attribute to existing Active
Directory site links, which Exchange Server 2007 servers will consider while routing between sites. This
is a cost value assigned to each IP site link evaluated by Exchange Server 2007. Messages will then be
routed based on lower - cost IP site links overriding existing Active Directory site link costs. This change
is made using the Set-ADSiteLink cmdlet.
As with the Routing Group Connector, Exchange Server 2007 SP1 now enables you to configure a
MaxMessageSize parameter for the ADSiteLink . A Non Delivery Report (NDR) is generated if a
message is over the specified limit.
To designate an Active Directory site as a Hub site, use the following cmdlet:
Set-AdSite -Identity ???Site A??? -HubSiteEnabled $true
To set the MaxMessageSize to the ADSiteLink use the following cmdlet:
Set-AdSiteLink -Identity DEFAULTIPSITELINK -ExchangeCost 25 -MaxMessageSize 50MB
Understanding Accepted Domains and
Email Address Policies
Before concluding this chapter, a few words on email address policies and accepted domains is required,
because these play a huge role in email address resolution and mail routing.
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