Exchange Online Modifies Retention Processing for Deleted Items Folder

Tweaks to How Exchange Online MRM Processes Microsoft Purview Retention Labels

Microsoft introduced messaging records management (MRM) in Exchange 2007. The first version of MRM was unsuccessful, but the second (in Exchange 2010) remains with us today in both the on-premises and online services. Much as Microsoft would like tenants to move away from Exchange Online MRM and embrace Microsoft Purview data lifecycle management (retention labels and policies), MRM retains some advantages that Purview can’t deliver today. Being able to move items to an online archive mailbox and folder-specific retention tags are the two most notable advantages.

There’s lots to like in Microsoft Purview data lifecycle management. Being able to use the same retention labels and policies for multiple workloads is a good thing. Advanced features like adaptive scopes (to identify sets of accounts or sites as target locations for policies) and manual disposition (invoke special processing when an item reaches the end of its retention period) are too. Being able to meld MRM and Microsoft 365 retention policies and labels in a retention strategy gives tenants a way to keep the advantages of MRM for targeted processing of mailboxes while moving most retention activity to Microsoft Purview. Maybe that’s why Microsoft surfaces Exchange MRM (albeit with a legacy tag) in the Compliance portal (Figure 1).

Exchange Online MRM in the Microsoft Purview Compliance portal
Figure 1: Exchange Online MRM in the Microsoft Purview Compliance portal

All of which brings me to message center notification MC567472 (2 Jun 2023), titled “Enhancing inherited and auto-applied retention label behavior in Exchange Online.” The post describes internal changes to how Exchange Online deals with labeled items when moving them to the Deleted Items folder (the change only applies to the Deleted Items folder). Microsoft plans to roll-out the change at the end of June and complete worldwide deployment by the end of August 2023.

Current Exchange Online MRM Behavior for Deleted Items

Until now, if a folder tag for Deleted Items is in the mailbox retention policy applied to a mailbox, Exchange Online applies that folder tag to items moved to Deleted Items. Hard deletions (SHIFT+DEL) move items direct to Recoverable Items and bypass Deleted Items, so the existence of a folder tag for Deleted Items doesn’t matter. The exception is when a user explicitly assigns an Exchange retention tag or a Purview retention label to an item. Manual assignments always take precedence over automatic assignments or inheritance from a folder tag. Items with manually-assigned tags are untouched when they move to Deleted Items.

New Exchange Online MRM Behavior for Deleted Items

The changes are subtle and give more priority to Purview labels, especially those applied by auto-label policies.

First, if an item has a Purview label which retains content (it has a retention setting for a set period, like 730 days), the Purview label remains in place regardless of what method (user or automatic process) applied the label. This happened before for manually-applied labels. The change is for labels applied by policy and ensures the retention of items for their full retention period.

For items with labels that don’t retain content but enforce a set action (like delete the item) when the label’s retention period lapses, processing follows these rules:

  • Items with a Purview label applied by an auto-label policy ignore the default folder tag applied to the Deleted Items folder. This avoids the chance that Exchange Online keeps items which an organization identifies for retention through an auto-label policy for their full retention period.
  • Items with an Exchange Online retention tag or Purview label inherited from the folder they move from to go to Deleted Items retain their label if the Deleted Items folder does not have a default tag. For instance, if the Inbox has a default folder tag with a retention period of 365 days, that tag stays with items moved from the Inbox to Deleted Items. When the Managed Folder Assistant (MFA) processes the items, it complies with the 365-day retention period and will not remove the items until this period lapses.
  • If the Deleted Items folder has a default folder tag, Exchange Online compares the retention periods for the retention labels or tags applied to items against the retention period defined in the default folder tag and acts based on the shortest deletion period.

Will Users Notice the New Retention Behavior?

I doubt that the average (or even not-so-average) end user will notice the change. Few people understand the complexities of Exchange MRM and possibly fewer the full spectrum of Microsoft Purview data lifecycle management. But it’s good to have consistent behavior and it seems like the tweaks Microsoft will introduce add some consistency to the mix of MRM and Purview.


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