Check which Transport Rule is being applied to an Email in Message Trace.

The PowerShell command below is used to identify the Transport Rule is applied to an email when checking in message trace: 

Get-TransportRule -Identity 1f56ba43-1cb9-4293-b24d-5e263a75fc8a | select description | fl

 Replace the identity with the code mentioned in the message trace. 

 Please refer to the below article for reference on Transport Rules : 

 https://docs.microsoft.com/en-us/powershell/module/exchange/get-transportrule?view=exchange-ps