404 error and a call to makeEwsRequestAsync fails from a server that has split CAS/MBX roles in Exchange Server 2013
Original KB number: 4476965
Summary
Consider the following scenario:
- You're running Exchange Server 2013 Cumulative Update 19 (CU19) or a later version.
- The server that's running Exchange Server is configured to have split Client Access server (CAS) and Mailbox server (MBX) roles.
- A Modern add-in calls the makeEwsRequestAsync function from any supported client, such as the Outlook client.
In this scenario, the call fails and returns a 404 error message.
Resolution
To fix this issue, install the CAS role on each Mailbox server. This is the preferred architecture for Exchange Server 2013.
Status
This is a known issue in Exchange 2013 CU19 and later versions.