In Exchange 2003 you needed to set the tarpit for exchange manually, but in Exchange 2007 you don’t have to. It defaults to a 5 second tarpit on all receive connectors. Since tarpits reduce spam, it may be a good idea to increase it in Exchange 2007. My personal preference is 10 seconds.
Get-ReceiveConnector | Select Name,TarpitInterval
You can also pipe it to all your connectors at the same time using this command:
Get-ReceiveConnector | Set-ReceiveConnector -tarpitinterval 00:00:10