M365 Changelog: (Updated) Microsoft Defender for Office 365 – updates to quarantine folder storage

MC383875 — Updated June 1, 2023: Microsoft has updated the rollout timeline below. Thank you for your patience.

Microsoft Defender for Office 365 is making some changes to quarantine folder storage. The experience for users will remain the same and users can leverage the delete action to maintain the storage folder for their quarantined messages.

This message is associated with Microsoft 365 Roadmap ID 93302.

When this will happen:

Standard: will begin rolling out in mid-June and be completed by mid-November (previously mid-September). – Complete

Government: will begin rolling out in mid-January 2023 (previously mid-November 2022) and be completed by late July 2023 (previously late May).

How this will affect your organization:

Non delivery report (NDR):

In the case that a user’s quarantine storage is full, new incoming messages routed to quarantine will be rejected and an NDR will be generated for those messages.

In the case of Zero hour Auto Purge, where malicious items need to be zapped from inbox to quarantine but there is no space, these messages will be instead, added to the junk mail folder.

Note: When there is a False positive Zero hour Auto Purge, messages wrongly moved to the Junk mail folder can be added back to their original location. 

New hard delete experience:

Previously, when messages were deleted by users from quarantine, those deleted messages could still be retrievable within a 30-day period after deletion was made. To help users better manage their storage, we will be introducing a hard delete experience whereby once the messages are hard deleted, they can’t be recovered. 

Hard delete experience
View image in new tab

Note: End users will only be able to delete quarantine messages that their Administrators has given them access to through the quarantine policy. 

What you need to do to prepare:

The goal for this communication is mostly for informational awareness. You may consider updating your training and documentation as appropriate.