Item count from Get-MailboxStatistics shows more items than Get-MailboxFolderStatistics

Original KB number:   3098973

Symptoms

Consider the following scenario.

• When you run the Get-MailboxFolderStatistics cmdlet on a mailbox, the number of items in each returned folder may not equal the total item count that's returned by the Get-MailboxStatistics cmdlet. The Get-MailboxStatistics cmdlet shows more items than the number that's returned by the Get-MailboxFolderStatistics cmdlet.
• When you run an eDiscovery search on a mailbox, the item count that's returned by the estimate option or the export option may not match the item count that's returned by the Get-MailboxStatistics cmdlet.

Cause

There are some folders in a mailbox that are marked with a special Internal Access flag. These folders are reserved for Microsoft internal use and aren't visible to users or administrators in your organization. Although the folders aren't visible, the item counts of the folders are returned by the Get-MailboxStatistics cmdlet. This behavior is by design.

More information

The Get-MailboxFolderStatistics cmdlet returns the aggregate count of folders that are visible to clients. Use the item counts in these folders to represent the total number of items that are visible to clients and to eDiscovery searches.

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