M365 Changelog: (Updated) Microsoft Defender for Office 365 Tenant Allow Block List limits

MC678057 – Updated October 20, 2023: Microsoft has updated the rollout timeline below. Thank you for your patience.

Soon, customers with Microsoft Defender for Office 365 plan 2 can create 10,000 block entries and 5,000 allow entries (via admin submissions) in the Tenant Allow Block List for each category (Domains & addresses, Files, and URLs). Customers with Microsoft Defender for Office 365 plan 1 can create 1,000 block entries and 1,000 allow entries (via admin submissions) in the Tenant Allow Block List for each category. Customers with Exchange Online Protection will remain at 500 block entries and 500 allow entries (via admin submissions) in Tenant Allow Block List for each category. The limit for spoofed senders will remain at 1,024 total entries (block entries and allow entries combined) for all service plans.

This message is associated with Microsoft 365 Roadmap ID 98185

When this will happen:

This change will start rolling out in late October 2023 (previously early October) and should be completed by late December 2023 (previously late November).

How this will affect your organization:

It would not affect any of your existing Tenant Allow Block List entries.

If you already have higher limits, then you will remain unaffected by this change.

If you have a mixture of licenses, Microsoft will consider the highest service plan as the service plan for the entire tenant and allocate Tenant Allow Block list limits.

What you need to do to prepare:

No changes are required. Your existing Tenant Allow Block List entries will not be affected. Once this change is made, you might be able to create more allow entries and block entries based on your service plan.