Web DAV system folder 'X' is missing: This error indicates that the mailbox is missing essential system folders or references to system folders are missing.
Resolution:
Make sure the mailbox is not full. Exchange will disable access to the drafts folder if the mailbox is full. If necessary, clear content from the mailbox (examples: deleted items, junk mail, etc.).
Verify that all system folders are present: inbox, outbox, drafts, sent items, deleted items, junk email, calendar, contacts, tasks. To verify that a folder is indeed a system folder, see if it can be deleted in OWA. For example, if there is a folder called "outbox" and deletion is possible, then the folder is probably just a regular folder called "outbox" - not the outbox system folder. System folders cannot be deleted.
If you are missing system folders, consider running Outlook in mailbox repair mode.
- Open a command prompt,
- Navigate to the directory where OUTLOOK.EXE resides (for example, C:\Program Files\Microsoft Office\Office14).
- Run the command: OUTLOOK.EXE /CleanProfile /ResetFolderNames /ResetFolders
Once the operation has completed, resubmit your mailbox for migration.