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Exchange 2016 – Mailbox corruption

Mailbox corruption often appears during mailbox migrations, as the migration process finds issues with old data in the mailbox that the end user never looks at any more.

However, end users will notice more obvious signs of mailbox corruption, such as:

  • Folders showing item counts that are incorrect (e.g. a folder display 1 unread item when there are in fact no unread items)
  • Search folders not displaying the correct results
  • Mailbox folders missing expected items from some views

If you suspect mailbox corruption, you can run a mailbox repair request in detect mode. Mailbox repair requests can be run for one or more of the following corruption types:

  • SearchFolder
  • AggregateCounts
  • FolderView
  • ProvisionedFolder

Mailbox repair requests can be run against a single mailbox, or an entire database. For example, to run a repair request for Mailbox:

“New-MailboxRepairRequest -Mailbox “TestUser” -CorruptionType SearchFolder,AggregateCounts,FolderView,ProvisionedFolder”

To run a repair request against an entire database, use the –Database parameter instead:

“New-MailboxRepairRequest -Database DB01 -CorruptionType SearchFolder”

Mailbox repair requests are background tasks, which will start and stop depending on the performance of the Exchange server and its load at the time.

Note: For performance reasons, only one database-level repair request or 100 mailbox-level repair requests can be active at the same time. Once a repair request has started, it can’t be stopped unless you dismount the mailbox database.

You can monitor the progress of your mailbox repair request by running the Get-MailboxRepairRequest cmdlet:

To view the results, look at the CorruptionsDetected and CorruptionsFixed properties of the repair requests:

For more information regarding the repair commands please check the following URL’s:



Ratish Nair

Microsoft MVP | Office Servers and Services

Team @MSExchangeGuru

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