The Exchange Server 2010 Edge Transport server role is automatically enabled for the built-in anti-spam features when it is installed. However some of the features require configuration before they can begin blocking spam.
The IP Block List Providers anti-spam feature is one example. It is enabled by default, but no block list providers are included in the configuration.
IP block list providers are an effective way to block the majority of spam, because they maintain comprehensive databases of IP addresses on the internet that are known and suspected spam sources. This allows an Exchange server to determine whether or not to block an incoming email during the initial stages of the SMTP connection, based on the IP address of the sending host.
Blocking spam at such an early stage of the communication sequence uses less bandwidth and processor resources than email content filtering, because the full email message is never transmitted to the Exchange server.
One of the best IP block list providers is Spamhaus. You can configure an Edge Transport server to use Spamhaus as an IP block list provider by following these steps.
Log on to your Edge Transport server and launch the Exchange Management Console. In the Anti-spam tab right-click IP Block List Providers and select Properties.
Select the Providers tab and then click Add.
Enter the Provider Name of Spamhaus and the Lookup Domain of zen.spamhaus.org.
Click OK and OK again to apply the change.
The Edge Transport server will now lookup the IP address of connecting hosts to determine whether or not to accept mail from them.