Transport
agents are part of the core Exchange Server functionality provided to
organizations that allow for policies to be enforced within the
messaging platform. Microsoft designed these policies with built-in
support for third-party add-ons. This allows other companies to build
products that directly integrate with Exchange Server 2010 to scan mail
and to run specific tasks on the mail that flows through the system.
At their core, Transport
agents are just a programmatic method of performing tasks on mail based
on a specified criterion. They can range in complexity from a simple
“Forward a copy of all emails sent to this person to this particular
email address” to “Apply this equation to this email message to
determine whether or not it is spam.”
Understanding the Role of Transport Agents in Policy Management
Transport
agents are especially important for companies looking to bring their
messaging platform into compliance with specific governmental
regulations, as some of the default transport agents, such as journaling
or mail retention policies, offer out-of-the-box functionality that is
required by many of these regulations. For situations where built-in
functionality might not suffice, the field of third-party add-ons to
Exchange Server 2010 transport agents is increasing every day, so
organizations can deploy a custom agent to perform a specific task.
Prioritizing Transport Agents
Exchange Server 2010
allows administrators to prioritize the order in which transport agents
act on a message. As an SMTP message passes through the transport
pipeline, different SMTP events are acted out. These events, with names
such as OnHeloCommand and OnConnectEvent,
happen in a specific order every time, and transport agents set to act
upon a specific event will only fire when that event has occurred. After
it occurs, however, the priority level can be set, determining which
transport agent acts first at that particular juncture.
Changing priority on a
specific transport rule is as simple as right-clicking on the rule in
the details pane and choosing Change Priority.
Using Pipeline Tracing to Troubleshoot Transport Agents
Pipeline tracing with
Exchange Server 2010 transport agents is a diagnostic tool that can be
used to send a copy of the mail message as it existed before and after a
transport rule went into effect. This copy is sent to a specific
mailbox.
To enable Pipeline tracing on an Exchange server, run the following command from the Exchange Management Shell:
Set-TransportServer Server5 –PipelineTracingEnabled $True
where
Server5 is the name of the server. To set a specific mailbox to be the
pipeline tracing mailbox, run the following command from the shell:
Set-TransportServer Server5 –PipelineTracingSenderAddress [email protected]
where Server5 is the name of the server and only mail from [email protected] is traced through the pipeline.
Pipeline tracing must
be enabled on all Hub Transport and/or Edge Transport servers in the
topology for it to be useful as a troubleshooting mechanism.
Outlining the Built-in Transport Agents in Exchange Server 2010
Exchange Server 2010
contains built-in support for a wide variety of transport agents. Some
of these agents run off of Hub Transport servers, and others run off of
Edge Transport servers.
The Hub Transport server role transport agents are as follows:
The Edge Transport server role transport agents are as follows:
Content Filter agent
Sender ID agent
Recipient Filter agent
Connection Filtering agent
Attachment Filtering agent
Address Rewriting Outbound agent
Address Rewriting Inbound agent
Edge Rule agent
Sender Filter agent
Protocol Analysis agent
