ECP cannot display more than 500 OUs


Recently a colleague of mine found an interesting issue with an Exchange Server 2013 organization setup.

The local service desk personnel wasn't able to select a target organizational unit (OU) when creating new mailboxes. The ECP dialogue just showed an empty window.


By default the ECP OU picker result set contains 500 entries only.

The OU picker does not query the Active Directory with -ResultSize Unlimited.


Microsot Knowledge Base article 3038717 provides the solution for this issue.

When querying the local Active Directory for the overall number of organization units using the following command, it turned out that the Active Directory contained more than 4.000 OUs.

(Get-OrganizationUnit -ResultSize Unlimited).Count

Use this cmdlet to determine the current number of organization units and define a reasonable number for querying Active Directory.

Add a new key node to the ECP web.config file on each of your Exchange 2013 servers.


The ECP web.config file is located in

  • $exinstallClientAccessecp

Saving a modified web.config normally triggers an application pool restart. If required, use the following one-liner to restart the ECP application pool across all Exchange 2013 servers.

Get-ExchangeServer | ? { $_.AdminDisplayVersion -like '*15.*'} | % { Invoke-Command -ComputerName $_.Name -ScriptBlock {Restart-WebAppPool MSExchangeECPAppPool } }


It has not yet been verified, if the issue is present with Exchange Server 2016 as well. If so, just let us know.


Keep enjoying the oddities of Exchange Server.





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