M365 Changelog: Microsoft Defender for Office 365: Update of blocked transport rule count volume in Mailflow status report

MC698146 – Microsoft is updating the aggregate count volume of blocked transport rule emails in Mailflow status report.  

When this will happen:

Standard: starting mid-December 2023

Government: starting late December 2023

How this will affect your organization:

Previously, the aggregate count of Transport rule email blocked that was shown in the Mail flow status report included the count of all filtered email that matched a transport (not necessarily blocked by the transport rule it matched)

Microsoft is updating this behavior to ensure that aggregate count of Transport rule emails blocked actually represent the total volume of emails that match a transport rule and was blocked by that transport rule.

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What you need to do to prepare:

As a result of this change, Admins will notice a reduction in the volume of emails that are blocked by transport rules which is shown in the Mail flow status report. This reduction is expected.

The purpose of this communication is for awareness. Admins should also update their training documentation as they see fit.