Understanding Transport Agents in Exchange 2013

Transport agents allow you to process / manipulate messages that go through the transport pipeline:

- Front End Transport service on Client Access Servers
- Transport Service on Mailbox Servers
- Mailbox Transport Service on Mailbox Servers

While there are a series of default (created by Microsoft) transport agents such as (to name a few):

- Malware Agent on the Mailbox Server
- Transport Rule Agent on the Mailbox Server
- Recipient Filter Agent on the Edge Server
- Sender Filter Agent on the Edge Server AND Mailbox Server.

Microsoft have also provided third-party vendors to create their own transport agents - for example anti-spam products.

Agents also have an assosiated priority so that a specific transport agent could process mail first. For example some custom transprot agents are required to run first - so we would make sure they have the highest priority e.g.

Set-TransportAgent -Identity "MyCustomTransportAgent" -TransportService -FrontEnd -Priority 100

We can get a list of transport agents with the following command:

Get-TransportAgents

and we can disable / enable a transport agent with:

Disable-TransportAgent "Test App" -TransportService Hub

Enable-TransportAgent -Identity "Test App" -TransportService Hub

You can find out which transport agents are triggered by which event with:

Get-TransportPipeline