Symptoms
Assume that accessing external Exchange Web Services (EWS) URL is blocked from internal Exchange servers in a Microsoft Exchange Server 2016 or Exchange Server 2013 environment. In this situation, the client applications that are posting ExecuteEwsProxy calls will be failed to connect, such as Salesforce add-in for Outlook and Outlook Web App (OWA).
Cause
This issue occurs because the ExecuteEwsProxy function is only using external EWS URL. This causes the makeEwsRequestAsync method fail to call EWS.
Resolution
For Exchange Server 2016, install Cumulative Update 8 or a later cumulative update for Exchange Server 2016.
For Exchange Server 2013, install Cumulative Update 19 or a later cumulative update for Exchange Server 2013.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.
Third-party information disclaimer
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
