A customer reports that messages and calendar items are visible in the root folder of their archive, even though they were not directly included (To/CC/BCC) in those items.
Upon review, it was observed that the user has delegate or Reviewer access to other users’ calendars, and that emails embedded within calendar events from those other users are appearing in their own archive view.
Messages not directly sent to or from the user appear in their archive root folder.
Calendar subfolders from other mailboxes are visible under the user’s Calendar in Outlook.
Emails embedded within those calendar invites are also visible in the user’s root archive folder.
This is expected behavior and is due to how MAPI (Messaging Application Programming Interface) exposes mailbox data to users with shared access permissions.
When a user has delegate or calendar permissions on another mailbox, Exchange exposes certain message properties to that user — including embedded or attached messages inside calendar events.
The Exchange Stubbing Module (ESM) processes mailbox items based on MAPI-level access scope, not only direct message recipients.
As a result, when a user has permission to view another mailbox’s calendar, ESM can detect and link those items as part of the user’s accessible mailbox hierarchy, even if the user is not a participant in the original message.
MAPI treats any accessible calendar or mailbox folder as part of the user’s message store if permissions are granted.
ESM enumerates these accessible items and associates them with the user’s archive according to message property relationships.
Therefore, embedded emails within shared calendar events appear in both:
The subfolder (under the shared user’s calendar), and
The root folder of the user’s archive.
User A has Reviewer access to User B’s calendar.
User B receives a meeting invite containing an email attachment.
Because User A can view User B’s calendar, MAPI exposes that event (and its attachment) to User A.
During ESM archiving, the item is linked under User A’s archive as a visible object, even though User A was not in the message’s recipient list.
This behavior is by design and consistent with how MAPI handles shared calendar and mailbox access.
To mitigate or control this behavior, consider the following options:
Restrict calendar permissions: Limit delegate or shared calendar access for users who should not see embedded messages.
Exclude folders from ESM: Configure ESM to skip specific shared folders or calendar paths from archiving.
Validate folder mappings: Confirm that renamed calendar subfolders do not interfere with archive hierarchy before migration.
This is an expected and documented behavior resulting from MAPI message exposure through delegate access.
Messages and calendar items appearing in the root folder of a user’s archive, even without direct inclusion, occur because ESM processes accessible folders via MAPI, not solely based on recipient data.
