Well the real fix would be to re-configure how AutoDiscover is set up on your Exchange Server/Outlook clients. For information on that, go to Exchange & The Autodiscover Web Service.
However your question asks specifically how to ignore certain URLs from being logged. I don't know of a way to do that, but I can suggest a way to have this request ignored.
First, make sure Attribute Routing is enabled.
And then add the following controller to your solution.
public class AutoDiscoverController : Controller
public ActionResult Index()
return new HttpStatusCodeResult(HttpStatusCode.RequestTimeout);
There is also a config level approach where you mark the above request to a static handler in IIS. As such, the request never makes it to your application.
<add name="AutoDiscoverXmlFileHandler" path="autodiscover.xml" verb="GET" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" responseBufferLimit="0" />
Source: Using a route to return 408 on a specific file name request