Office 365 – Moving online mailbox to on premise failed with error Resource ‎’CiAgeOfLastNotification‎(System)‎‎’ is unhealthy and shouldn‎’t be accessed

Recently, I went to an error when moving online mailboxes from Office 365 – Exchange Online – to on premises – Exchange 2013.
Strangely, these mailboxes have been moved multiple times in both direction – on premises to online and online to on premises – without any issue.
The migration batch starts and content is being synchronized between Exchange Online and Exchange On Premises and finally the job failed with the error
Error: MigrationPermanentException: Error: Resource ‎’CiAgeOfLastNotification‎(System)‎‎’ is unhealthy and shouldn‎’t be accessed
After some digging, the issue was due to a corrupted index on Exchange On Premises.


  • On the Exchange server which host the mailboxes databases, stop the following services
    • Microsoft Exchange Search
    • Microsoft Exchange Search Host Controller
  • Using Windows Explorer, browse to the location where the index are located
    • This is a subfolder named with a GUID below the folder where the database file is stored
    • To get to the path to the database, run the PowerShell command Get-MailboxDatabase | fl *path*
  • Delete the folder with a GUID – BE CAREFUL don’t delete anything else
  • Restart both services and wait few minutes until the Fast engine starts indexing again
  • Then start again your migration

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