Bogus Public Folder Mailbox Quota Alerts in Exchange 2013

All is not quiet on the Exchange 2013 front if you are running Public Folders. Once you migrate from legacy PFs, ( I assume you aren’t crazy enough to start using Public Folders in a greenfield 2013 org), you may start seeing over Managed Availability Alerts such as:

Log Name:      Microsoft-Exchange-ManagedAvailability/Monitoring
Source:        Microsoft-Exchange-ManagedAvailability
Date:          1/26/2016 8:30:31 AM
Event ID:      4
Task Category: Monitoring
Level:         Error
User:          SYSTEM
The public folder mailbox PFMBX01 is approaching its storage limit. Consider splitting the mailbox using Split-PublicFolderMailbox.ps1. This warning will not be sent again for at least twenty four hours. 
At this point, you may be tempted to move folders from this mailbox to another.

However, before you do that, check the actual quota usage either in EAC:



Or powershell:

Get-MailboxStatistics <PFMBX> |FL totalitemSize

TotalItemSize : 14.2 GB (15,248,828,208 bytes)

So what’s going here? Why are alerts firing when the mailbox quota warning has not been reached? Quite simply, it’s a bug.

The MA service doesn’t or can’t differentiate between individual folders that are nearing their quota and the actual Public Folder Mailbox. For the admin, this can create a lot of confusion. If an individual folder is nearing quota, the folder contacts will get alerted and that is typically sufficient. If the mailbox itself is nearing it’s quota warning level, the admin will obviously want to take action soon.

Hopefully this will be fixed in Exchange 2013 with a future CU.

For 2016, I will update this blog when I have time to test.

If you are concerned about missing actual PF mailbox over quota events, I suggest creating a scheduled PowerShell task that checks the mailbox sizes and fires off an email alert if the quota is approached.




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