Few of our customer reported that they are getting HTTP 404 Error reported; when they tries to use EWS HTTP service endpoint for their application for Exchange Server 2010. However, the same application work fine with EWS HTTP service endpoint with Exchange Server 2007 without any issue.
If we go into Internet Information Services (IIS) on Exchange 2010 RTM and uncheck the box ‘Require secure channel (SSL)’ on the EWS virtual directory. And then we attempt to make a request using HTTP using EWS service endpoint as “http://host:port/EWS/Exchange.asmx” then we would receive a HTTP 404 Resource Not Found.
Exchange 2010 Web Services are now based on Windows Communication Foundation (WCF). We receive a HTTP 404 because WCF attempts to locate the endpoint for HTTP but cannot find it and throws a System.ServiceModel.EndpointNotFoundException exception which throws up to the client as a 404 exception.
Using HTTP instead of HTTPS is not the recommended approach for Exchange Web Services but sometimes it is helpful in debugging/troubleshooting to have this option.
Here are the steps posted by my colleague Dave @ How to configure a HTTP endpoint for Exchange Web Services in Exchange 2010 to workaround the issue.