Transport Rules Test

Using transport rules, you can look for specific conditions in messages that pass through your organization and take action on them. Transport rules let you apply messaging policies to email messages, secure messages, protect messaging systems, and prevent information leakage.

The basic workflow for transport rules is as follows:

  • You use the Exchange admin center (EAC),the Shell, or a DLP policy to create a transport rule. After you create your rule, it is stored in Active Directory.
  • As messages go through the transport pipeline, the Transport rules agent is invoked. The Transport rules agent is a special Transport agent that processes the Transport rules you create.
  • The Transport rules agent evaluates the message, and if the message fits the conditions you specify in a transport rule, it takes the specified action on that message based on the mode of the rule.

If these transport rules are not configured properly, then the rules agent will report errors during evaluation, causing messages to be deferred. This in turn will disrupt mail flow and adversely impact end-user experience with the mail server. To ensure uninterrupted mail flow, administrators will have to capture these errors promptly and reconfigure transport rules rapidly. For this, administrators can use the Transport Rules test. This test monitors transport rules and instantly notifies administrators if messages are deferred owing to evaluation errors. This way, the test prompts administrators to quickly reconfigure/remove/disable transport rules so as to avert message deference.

Target of the test : A Microsoft Exchange 2013/2016 server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for the Exchange server being monitored

Configurable parameters for the test
  1. Test period - How often should the test be executed
  2. Host - The host for which the test is to be configured.
  3. port – The port at which the host listens.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Messages deferred due to rule evaluation errors:

Indicates the number of messages that were deferred due to errors in rule evaluation.


A high value indicates that one/more transport rules are poorly configured are hence causing many errors during evaluation. You need to identify such transport rules and reconfigure them, remove them, or disable them to reduce the value of this measure drastically.  

Messages deferred rate:

Indicates the rate at which messages were deferred owing to errors in rule evaluation.


A consistent increase in this value is a cause for concern, as it indicates that transport rules are throwing errors during evaluation causing frequent deference of messages.