Cloud Service for Email (Reflecting Mode) - duplicate messages in journaling

Products

• Data Loss Prevention Cloud Service for Email

Issue/Introduction

You've recently implemented the Cloud Service for Email in O365, Reflecting Mode.

You have journaling set, and notice that messages sent to Cloud Service for Email are journaled twice - once when the message is sent to the Cloud Service, and once when it returns to O365. 

Is there a way to prevent this from occurring?  

Environment

Release : 15.8

Component :

Cause

Various

Resolution

Look to the following article on Microsoft - specifically in the "Troubleshooting" section, where you can see this behavior might occur for any external cloud service:

Journaling in Exchange Online | Microsoft Docs

By following those guidelines, customers have effectively reduced, if not altogether eliminated, journaling duplicates.