Something more about Exchange 2007

Send Connectors and Receive Connectors

One Receive connector is configured to receive SMTP traffic from all sources by listening on Port 25. A second Receive connector is configured to receive SMTP traffic from non-MAPI clients by listening on Port 587. The Client Access server role provides the IMAP4 and POP3 protocols for non-MAPI clients.

Edge Transport Server Co-Existence
You can add an Edge Transport server to an existing Exchange organization without upgrading the internal Exchange servers or making any organizational changes. You do not have to perform any Active Directory preparation steps when you install the Edge Transport server. If you are using the Exchange Intelligent Message Filter in Exchange Server 2003 to perform anti-spam tasks, you can use the Edge Transport server to provide an additional layer of anti-spam protection. The Edge Transport server provides antivirus and anti-spam protection as messages enter the network.

When an Edge Transport server is deployed to support an Exchange organization that has not yet deployed Exchange 2007, a limited set of features are available. You can’t create an Edge Subscription in this scenario. Therefore, you cannot use the Recipient Lookup or safelist aggregation features.

 

To get more details please visit the following url.

http://technet.microsoft.com/en-us/library/aa998186(EXCHG.80).aspx