In effect, this is the same processing as would occur if you were able to assign a 1-day move to archive Exchange retention tag to these folders. The change described in MC288630 and being rolled out in mid-October aims to take advantage of archive mailboxes by moving information from the Purges, Versions, and DiscoveryHolds sub-folders to the archive mailbox one day after their generation. Although Microsoft allocates a 100 GB storage quota to store data in Recoverable Items when a mailbox is subject to retention, it’s not uncommon to find that some mailboxes accumulate information quickly and occupy the quota. The point of retention policies is to keep information for as long as it is needed. For more information on how these folders are used, see this Microsoft article. During this period, users can recover items from Deletions using Outlook’s Recover Deleted Items option. Items stay in Deletions for the deleted items retention period defined for a mailbox (usually 14 days but can be changed to a maximum of 30 days). You will see items in the Deletions folder because this is where items removed from the Deleted Items folder go until Exchange Online removes them permanently. If a mailbox doesn’t come within the scope of a litigation or in-place (retention) hold, you won’t see items in these folders. SubstrateHolds: Contains the original versions of items managed by the Microsoft 365 substrate (for example, compliance items for Teams messages).DiscoveryHolds: Contains hard-deleted items.

Versions: Stores the original versions of edited items.

Purges: Stores items removed from the Deletions folder.

A set of sub-folders within Recoverable Items are used for retention processing:

The Recoverable Items structure is composed of several sub-folders, each with a distinct task. It’s a classic example of how poor editing can mask the value in a message. What does “ Exchange online auto-expanding archive–Automatic archive of mailbox items in Purges, Versions and Discovery Holds folders” mean? That’s exactly what I thought when I read message center notification MC288630 (1 October). Odd Title for Notification, but Real Value in Update

Exchange online deleted items recovery