When using a standard SSL certificate for Webmail and not using a UC certificate you are likely to get SSL “mismatch” errors.
This is how you can fix that :
Set-WebServicesVirtualDirectory -Identity “EWS*” -ExternalUrl “Https://<external webmail address>/EWS/Exchange.asmx” -InternalUrl “Https://<external webmail address>/EWS/Exchange.asmx”
Set-ClientAccessServer -Identity <CASservername> -AutoDiscoverServiceInternalUri https://<<external webmail address>
