Exchange Online Protection (EOP) assigns a bulk complaint level (BCL) to inbound messages from bulk mailers. A higher BCL indicates a bulk message is less likely to be wanted by the user.
We are rolling out several changes in how we allocate BCL scores to messages to provide more accurate scoring and coverage for bulk messages. We are also updating the threshold for the strict policy from 4 to 5 to better align with the new scoring. In addition, customers using Microsoft Defender for Office P2 or customers with E5 licenses will be able to view the BCL score for a message in advanced hunting.
When this will happen
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We will begin rolling out in mid-November and expect to complete rollout by late January 2023.
How this will affect your organization
This change is expected to improve the handling of bulk messages within your organization and should not impact users. In the case of aggressive bulk settings where the threshold is 4 or less, may result in wanted bulk messages being called bulk and it is recommended that such policies be reviewed.
What you need to do to prepare
There is nothing you need to do; however, it is good practice to review your Antispam policies to ensure that you have an appropriate value for BCL, particularly if you have a threshold of 4 or less.
To learn more about how to tune your tenant’s bulk thresholds visit this documentation (What’s the difference between junk email and bulk email in EOP? > How to tune bulk email).
Message ID: MC467231
Product: Defender, Exchange, Microsoft 365 Defender
Platform: Online, World tenant