Mailboxes on a recently recovered multirole (Client Access and Mailbox) server that is running Microsoft Exchange Server 2013 cannot access the free/busy service.

When this problem occurs, the following errors are logged.

Outlook logs (Outlook.etl files):

Exception: Proxy web request failed. , inner exception: The request failed with HTTP status 404: Not Found.
Server Name: < problematic server>
Exception Type: ProxyWebRequestProcessingException
Response Code: ErrorProxyRequestProcessingFailed

IIS Logs on the problematic server:

POST /ews/exchange.asmx - 443 – <Client-IP> ExchangeInternalEwsClient-AuditLog - 404 0 0 15
POST /ews/exchange.asmx - 443 - <Client-IP> ExchangeInternalEwsClient-AuditLog - 404 0 0 15
POST /ews/exchange.asmx - 443 - <Client-IP> ASProxy/CrossSite/Directory/EXCH/15.00.0847.030 - 404 0 0 0
POST /ews/exchange.asmx - 443 - <Client-IP> ASProxy/CrossSite/Directory/EXCH/15.00.0847.030 - 404 0 0 0


This problem occurs because the InternalNLBBypassUrl value is changed incorrectly after a disaster recovery operation is done on this Exchange 2013 multirole server.


To fix this problem, correct the InternalNLBBypassUrl value for Exchange Web Services (EWS) on the problematic server. The correct InternalNLBBypassUrl value should be the following:

https://<problematic server's fqdn>:444/ews/exchange.asmx

To do this, use one of the following methods.

Method 1

Use ADSIEdit to change the InternalNLBBypassUrl value for EWS for this problematic server. Then, recycle the MSExchangeServicesAppPool application pool in IIS. After you recycle the application pool, EWS should work as expected.

Method 2

Use Windows PowerShell to change these settings.

Note Window PowerShell returns a “not within a valid server write scope” error message.

  1. Start Windows PowerShell.

  2. Add the Exchange snap-in. To do this, run the following command:

    Add-PSSnapin *exchange*

  3. Run the following command:

    Set-WebServicesVirtualDirectory -Identity "<problematic server>\EWS (Exchange Back End)" -InternalNLBBypassUrl https://<FQDN of the problematic server>:444/ews/exchange.asmx

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