When multiple versions of Microsoft Exchange Server coexist within your organization, for instance during an upgrade, multiple versions of the Exchange Web Services (EWS) APIs may need to be used. This article describes the relevant configuration options.
When you are upgrading your existing Exchange organization, multiple Exchange Web Services (EWS) servers may need to be addressed.
The lowest Exchange version should be used in the ExchangeVersion key.
For instance in a coexistence scenario where Exchange 2010 SP3 and Exchange 2013 SP1 CU5 run in the same Exchange Organization, "ExchangeVersion" should be set to 'Exchange2010_SP2' in "C:\Program Files (x86)\ZyLAB\EDiscovery\Synchronization\Exchange\ExchangeService\ZyLAB.EDiscovery.Exchange.Standalone.WinService.exe.config" (default path).
Additionally, in some Microsoft Exchange Server coexistence implementations, queries originally directed to an Exchange Web Services (EWS) server may be redirected to a second EWS server on a higher version. In this case the AllowUsingHigherExchangeVersion option can be added to the appSettings section of the same configuration file:
"C:\Program Files (x86)\ZyLAB\EDiscovery\Synchronization\Exchange\ExchangeService\ZyLAB.EDiscovery.Exchange.Standalone.WinService.exe.config".
This is an example of how the configuration file should look like.
<add key="AllowUsingHigherExchangeVersion" value="true"/>
6.1; 6.1 Service Pack 1; 6.1 Service Pack 2; 6.2; 6.2 Service Pack 2; 6.3; 6.4