Exchange Server doesn't display all OUs when it creates a new mailbox

Applies to: Exchange Server 2016 Enterprise EditionExchange Server 2016 Standard EditionExchange Server 2013 Enterprise


When you create a new mailbox together with a new user account in Exchange Server, the complete list of organizational units (OUs) is not displayed as expected.


Exchange Control Panel (ECP) can display no more than 500 OUs. When there are more than 500 OUs, a new window is generated, and this window is either blank or contains a "There are more items to show in this view" message.


To resolve this issue, follow these steps:
  1. Determine the number of OUs on the Exchange Server mailbox server. To do this, run the following command in a shell:
    (Get-OrganizationalUnit –ResultSize unlimited).count
  2. On the Exchange Server mailbox server, go to the following folder:
    drive:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\ecp
  3. Add the following lines in the web.config file just above </appsettings>:
    <!-- allows the OU picker when placing a new mailbox in its designated organizational unit to retrieve all OUs - default value is 500 --><add key="GetListDefaultResultSize" value="500" /> 
    Note The value of GetListDefaultResultSize key should exceed the number of OUs that you found in step 1. Additionally, you will have to add this value every time that you install a cumulative update.
  4. In IIS Manager, restart the MSExchangeECPAppPool application pool.