Symptoms
Assume that you deploy Directory Synchronization for Office 365 in a Microsoft Exchange Server 2013 environment. When you use the New Remote Mailbox wizard in Exchange Admin Console (EAC), the organizational unit picker is not available.
Cause
This issue occurs because of a logic issue in Exchange Server 2013.
Resolution
To fix this issue, install cumulative update 10 for Exchange Server 2013.
Workaround
To work around the issue, use the New-RemoteMailbox cmdlet that contains the OnPremisesOrganizationalUnit parameter to create remote mailboxes.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.