Imminent Change to Microsoft Teams Private Channel Storage
Sep 16 2025
Teams private channels enable collaboration among a subset of a team’s members. While posts and messages exchanged on most Teams channels have historically been stored in the Exchange Online mailbox associated with the team, private channel communications have been stored in the Exchange Online mailboxes of all members of the private channel. See eDiscovery (Premium) workflow for content in Microsoft Teams. As early as September 20, this will change. Once Microsoft rolls out this change to your tenant, Teams private channel messages will be stored in the group mailbox associated with the team in question.
| Teams Message Category | Current Message Storage | Message Storage On/After September 20 |
| 1:1 and Group Chats | Exchange Online mailboxes of all chat participants | |
| Standard Channels | Exchange Online mailbox associated with parent team | |
| Shared Channels | Group mailbox associated with shared channel1 | |
| Private Channels | Exchange Online mailboxes of all private channel members | Group mailbox associated with private channel1 |
1 To preserve or search for messages sent in a shared channel (or in a private channel after this change), specify the Exchange Online mailbox for the parent team.
TIMELINE
The transition is expected to start by September 20. Organizations may experience the change at any point between September 20 and mid-December.
IMPACT
eDiscovery
- For existing Purview eDiscovery holds scoped to capture Teams private channel messages stored within one or more private channel participants’ mailboxes, consider rescoping the holds to also include the corresponding team group mailbox before September 20 to preserve new private channel messages.
- For new Purview eDiscovery holds and Purview eDiscovery searches that implicate private channel content and span a date range that straddles this backend storage change, include both the private channel participants’ mailboxes and the corresponding team group mailbox within the scope of the hold and/or search to ensure all intended content is preserved and/or identified.
Data Lifecycle Management
- It will no longer be possible to create new private channel-specific retention or deletion policies in Purview’s Data Lifecycle Management module. Instead, “Teams channel message” policies will also include private channel messages.
- Review all current retention policies designed to govern the retention or disposition of Teams messages, and consider appropriate policy revisions to ensure consistent future treatment of private channel messages.
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We know these changes can be disruptive to your workflows and are available to help support your assessment and mitigation efforts. If you have any questions or need assistance, please reach out to eMerge Information Governance.