Sharepoint Managed Paths
In case you are using Sharepoint Team Services; and have extended your Default Web Site, you will be unable to access web sites that are created as Virtual folders. Recently on one server, its administrator installed Exchange Server and was facing problem of receiving HTTP 404 – Path Not Found, when opening Outlook Web Access at http://exchangeserver/exchange URL.
You either remove Sharepoint extensions from Default Web Site, or add virtual directories as Excluded Path in Sharepoint Managed Paths.
Sharepoint Managed paths, are the URIs that Sharepoint will not handle/monitor. Sharepoint basically plugs into the HTTP request/response pipeline. If it receives requests containing such paths, it will simply not handle them and pass them on to next processor.