Consider the following scenario:
- You have a hybrid deployment of Microsoft Exchange Online in Microsoft Office 365 and of on-premises Microsoft Exchange Server that contains Microsoft Exchange Server 2013 and Microsoft Exchange Server 2007. Or, two organizations are federated, and at least one of them has Exchange Server 2007.
- Exchange Server 2013 has Cumulative Update 5 installed.
- Exchange Server 2013 and Exchange Server 2007 have different external Exchange Web Services (EWS) URL namespaces.