You are unable to choose the OU in EAC when creating a new Mailbox or Groups…

If you have more than 500 Organization Units in your AD forest, you may..no…you will, run into this issue in the Exchange 2013 EAC when creating a new mailbox or group and want to create the object in a different OU other than the default “Users” container.

Upon accessing the OU Dialog box:

OUBrowse

 

You will see this lovely message:

OU

Unfortunately, this is a known issue. There is no fix yet.

I would recommend you simply create the mailboxes and groups in Powershell if you want to specify the OU.

The work-around for EAC:

  •  Edit the web.config file on the MAILBOX server under

     \\Program Files \ Microsoft \ Exchange Server \ V15 \ ClientAccess \ ecp \

    add the following under the appsettings section of the file.

    <add key=”GetListDefaultResultSize” value=”<number more than OUs in your forest” />

Recycle ECP app pool.

Note that you will need to do this after each Cumulative Update.

 

P.S. If you do not know how many OUs your forest has:

Get-OrganizationalUnit -ResultSize unlimited | Measure-Object

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