In Exchange 2007/2010, the Edge Transport server role is deployed in your organization's perimeter network as a stand-alone server or as a member server of a perimeter-based Active Directory domain. Designed to minimize the attack surface, the Edge Transport server handles all Internet-facing mail flow, which provides Simple Mail Transfer Protocol (SMTP) relay and smart host services for the Exchange organization. Additional layers of message protection and security are provided by a series of agents that run on the Edge Transport server and act on messages as they are processed by the message transport components. These agents support the features that provide protection against viruses and spam and apply transport rules to control message flow.
The message-processing scenarios that you can manage on the Edge Transport server role are described in the following sections.
Internet Mail Flow
Servers that run the Edge Transport server role accept messages that come into the Exchange 2007/2010 organization from the Internet. After the messages are processed by the Edge Transport server, they are routed to Hub Transport servers inside the organization. All messages that are sent to the Internet from the organization are routed to Edge Transport servers after the messages are processed by the Hub Transport server.
Anti-Spam and Antivirus Protection
In Exchange 2007/2010, the anti-spam and antivirus features provide services to block viruses and spam, or unsolicited commercial e-mail, at the network perimeter. Most viruses use spam-like tactics to gain access to your organization and to entice users to open an e-mail message. If you can filter out most of your spam, you are also more likely to capture viruses before they enter your organization.
Spammers use a variety of techniques to send spam into your organization. Servers that run the Edge Transport server role help prevent users in your organization from receiving spam by providing a collection of agents that work together to provide different layers of spam filtering and protection.
Edge Transport Rules
Edge Transport rules are used to control the flow of messages that are sent to or received from the Internet. The Edge Transport rules help protect corporate network resources and data by applying an action to messages that meet specified conditions. These rules are configured for each server. Edge Transport rule conditions are based on data, such as specific words or text patterns in the message subject, body, header, or From address, the spam confidence level (SCL), or attachment type. Actions determine how the message is processed when a specified condition is true. Possible actions include quarantine of a message, dropping or rejecting a message, appending additional recipients, or logging an event. Optional exceptions exempt particular messages from having an action applied.
You use address rewriting to present a consistent appearance to external recipients of messages from your Exchange 2007/2010 organization. You configure the Address Rewriting agent on the Edge Transport server role to enable the modification of the SMTP addresses on inbound and outbound messages.
If any of these critical services were to fail – for instance, say the Edge Transport server processes internet messages very slowly – it can cause significant delays in the delivery of important mails to specified recipients. In the world of business, such slip-ups are inexcusable, as prompt and effective email correspondence is essential to win orders and earn customer goodwill. Therefore, to prevent such adversities and their impact on corporate revenues, the Edge transport server will have to be monitored 24 x 7, and problems in its operations should be reported to administrators proactively. This can be achieved using eG Enterprise.