In some cases, while migrating users to exchange online, I came across error while running Get-MoveRequestStatistics which said "Need Approval" . NeedApproval is not linked to a migration user but a time when migration would occur, for example in my case it was 10 PM every day. You could wait til the time and let it complete itself. Before reaching 10 PM it would show "Synced" and percentage completion would be 95%. In case you wish to complete it right away, you can run the below command. Set-MoveRequest -Identity <email address> -SkippedItemApprovalTime $(Get-Date).ToUniversalTime() It will now perform the last Incremental Sync and complete the migration.

Scenario: I was trying to export multiple mailboxes to PST files in bulk using a CSV file and ended up with error on 3 mailboxes. The error stated, the mailbox quarantined and unable to open message store. Cause: One of the reasons could be that Exchange identifies if a particular mailbox is consuming a lot of CPU power at a particular time, maybe because it has some bad items or unindexed items or corruption or may have a huge mailbox size. Upon identifying such mailboxes, Exchange server will put these mailboxes in Quarantine to avoid further consumption. When a mailbox is quarantined, it becomes inaccessible to the user and senders will receive an NDR stating the user is quarantined. Solution: Quarantine mailboxes cannot be removed from ECP just like Exchange Online. You need to remove the keys from Registry Editor. Follow below steps to remove the mailbox from quarantine. Fetch the GUID of the mailbox. Now fetch the GUID of databases where the mailboxes are hosted. Now open regedit.exe and navigate to "HKLM\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<ServerName>\Private-{db guid}\QuarantinedMailboxes\{mailbox guid}" Under QuarantinedMailboxes you will find GUID of mailboxes that have been quarantined. You can delete those keys and exit regedit. Now you need to restart IIS for it the take effect. To reset IIS, type IISRESET /Restart This can fix your issue. Alternatively, instead of restarting IIS you can dismount and remount the database or apart from this you can also modify the crash count value in the CrashCount Key to 2. A second method is to run the following command in EMS: Disable-MailboxQuarantine <Mailbox Name> Now you can perform repairs on the mailbox using New-MailboxRepairRequest cmd.