Delete a Microsoft 365 account and the person's Copilot history does not vanish with their sign-in. Learn's Copilot retention page is direct: if a user leaves and their account is deleted, Copilot and other AI app messages that are subject to retention are stored in an inactive mailbox. They stay under the retention policy that applied before the mailbox went inactive, and they stay searchable in eDiscovery.
Our leaver post covered the three clocks on mailbox, OneDrive and flows. This one is narrower: what happens to Copilot prompts and responses under retention when the person is gone, and who owns that clock versus the deletion that creates the inactive mailbox.
Where Copilot interactions already live
Before anyone leaves, Copilot prompts and responses are copied into a hidden folder in the mailbox of the user who ran the AI app. Compliance staff search it with eDiscovery; ordinary admins don't browse it. The same Exchange timer jobs evaluate those items, move expired ones to SubstrateHolds, and permanently delete them only when nothing else holds them.
Copilot retention was always mailbox retention with a different front end. When the person leaves, that design decides the outcome.
What "subject to retention" means for an inactive mailbox
Learn's inactive mailbox guidance and the Copilot retention page together set the conditions:
- A hold or a retain (or retain-and-then-delete) setting must already apply when the Microsoft 365 account is deleted. Delete-only retention does not create an inactive mailbox. Neither does an Exchange MRM policy.
- Copilot messages under retention follow the mailbox into the inactive state, remain under the policy that applied before, and remain available to eDiscovery.
- Confirm the hold or retention has actually applied before you delete the account. Otherwise you get a soft-deleted mailbox with a 30-day recovery window, not an inactive mailbox kept for the retention period.
- Don't rename the user principal name or primary SMTP address first. Learn warns that changing those before deletion can block you from removing the inactive mailbox later.
Adaptive policy scopes can target inactive mailboxes on purpose, so former employees can carry a different retention period from current staff. That is a records decision for leavers' Copilot history as much as for their email.
One documentation note: the inactive mailboxes page still lists the older location name "Teams chats and Copilot interactions." The Copilot retention page is the one that states Copilot messages under retention land in an inactive mailbox. After 15 January 2027, that coverage has to come from a Microsoft Copilot experiences policy, not a legacy combined Teams policy.
Two clocks, two owners
The retention clock starts when the prompt or response is created. Learn uses creation timing for Copilot locations the same way it does for Teams messages. The clock keeps running after the person leaves; deleting the account changes where the content is stored, not whether retention still applies. The records owner sets how long leavers' Copilot interactions must be kept, including any different period for inactive mailboxes through an adaptive scope.
The deletion clock is the offboarding step that removes the Microsoft 365 account. That is what converts a held mailbox into an inactive one, or what starts the 30-day soft-delete if nothing holds it. Identity and Exchange own the mechanics. They should not run that step until retention on the Copilot location (and any Litigation or eDiscovery holds counsel still needs) is confirmed applied.
If the only "hold" on a leaver was an eDiscovery case, Learn's standing warning still applies: when the case closes or the hold is released, an inactive mailbox held only by that case is permanently deleted. Use Microsoft 365 retention for leavers you must keep, including their Copilot history.
What to put in the offboarding checklist
- Records owner confirms a retain or retain-and-delete policy covers Microsoft Copilot experiences for that person (or an adaptive scope for once they are inactive).
- Compliance administrator verifies the policy is applied before anyone deletes the account.
- Counsel confirms any case holds that must survive offboarding, knowing a case hold is a poor long-term home for an inactive mailbox.
- Only then does identity delete the account.
The leaver ticket can still close in a day. The Copilot prompts they typed do not. Those sit in an inactive mailbox until the retention you set says otherwise.
