Forum Discussion
Exchange 2019 Mailbox Migration Error - Folder conflicts with Exchange Online folder
Hi Exchange Experts,
I'm migrating a small Exchange 2019 environment to 365. Been pulling my hair out becuase of just one mailbox giving this error
Error description ---------------------------
Error: AggregateMailboxFolderConflictPermanentException: The folder 'Files' conflicts with Exchange Online folder 'Files', please move the messages to another folder and restart the job.
Data migrated: 0 B (0 bytes)
Migration rate:
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Migration user report:
5/14/2025 12:32:05 PM [MEUP300MB0105] Request processing continued, stage CreatingFolderHierarchy.
5/14/2025 12:32:05 PM [MEUP300MB0105] Stage: CreatingFolderHierarchy. Percent complete: 10.
5/14/2025 12:32:12 PM [MEUP300MB0105] Stage: CreatingFolderHierarchy. Percent complete: 10.
5/14/2025 12:32:12 PM [MEUP300MB0105] Fatal error AggregateMailboxFolderConflictPermanentException has occurred.
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It seems to be a system folder and I've tried to remove files from it (although there're no files in it) using MFCMAPI tool with no success. Renamed the folder and tried to re-run the migration with no luck.
Has anyone experience this issue? any thoughts or tips are much appreciated !
Thank you.
5 Replies
Have you had a resolution to this error? I am seeing the same thing but the Files folder looks to be in all mailboxes, not sure why one or two are failing me with the same error you see.
I manage to resolve this by renaming "Files" to "MyFiles" and unhid the folder thru MFCMAPI tool (PR_ATTR_HIDDEN = False)
Hi Curious_Kevin16,
I managed to resolve this by renaming the "Files" folder to "MyFiles" and unhide the folder using MFCMAPI (PR_ATTR_HIDDEN = False).
My guess is that the user has created a folder called "Files" in their mailbox and this is conflicting with the system folder in EXO. Maybe have a chat to the user and see if they can rename it.
"Files" seems to be a system folder and you can't do much except renaming which we tried through MFCMapi with no luck, it still refers to the "Files' folder.
EXO shouldn't matter should it? as we're simply trying to remote move the mailbox and obviously there's no mailbox exists in EXO for this user yet.
