OWA -Out of office Reply

Which version of Exchange and outlook you are using

Exchange 2010 sp1 and outlook 2010. This is running in coexistence with exchange 2003

Solution from Adam on the link above may help
"had a host header in the site bindings for the default web site in IIS. Not sure why or how that got there. Removing that, run iisreset from cmd prompt and it's now working again. "

OR

http://support.microsoft.com/kb/941146

http://blogs.technet.com/b/exchange/archive/2010/09/01/3410888.aspx

I have tried all these. I haven't got a host header in the site bindings for the default website. Nothing works. I am running SP1 and all hotfixes have been applied.

Description:
WebHost failed to process a request.
 Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/25879650
 Exception: System.ServiceModel.ServiceActivationException: The service '/ecp/Organize/AutomaticReplies.svc' cannot be activated due to an exception during compilation.  The exception message is: Security settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service.. ---> System.NotSupportedException: Security settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service.
   at System.ServiceModel.Channels.HttpChannelListener.ApplyHostedContext(VirtualPathExtension virtualPathExtension, Boolean isMetadataListener)
   at System.ServiceModel.Channels.HttpTransportBindingElement.BuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener[TChannel]()
   at System.ServiceModel.Channels.MessageEncodingBindingElement.InternalBuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.WebMessageEncodingBindingElement.BuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener[TChannel]()
   at System.ServiceModel.Channels.Binding.BuildChannelListener[TChannel](Uri listenUriBaseAddress, String listenUriRelativeAddress, ListenUriMode listenUriMode, BindingParameterCollection parameters)
   at System.ServiceModel.Description.DispatcherBuilder.MaybeCreateListener(Boolean actuallyCreate, Type[] supportedChannels, Binding binding, BindingParameterCollection parameters, Uri listenUriBaseAddress, String listenUriRelativeAddress, ListenUriMode listenUriMode, ServiceThrottle throttle, IChannelListener& result, Boolean supportContextSession)
   at System.ServiceModel.Description.DispatcherBuilder.BuildChannelListener(StuffPerListenUriInfo stuff, ServiceHostBase serviceHost, Uri listenUri, ListenUriMode listenUriMode, Boolean supportContextSession, IChannelListener& result)
   at System.ServiceModel.Description.DispatcherBuilder.InitializeServiceHost(ServiceDescription description, ServiceHostBase serviceHost)
   at System.ServiceModel.ServiceHostBase.InitializeRuntime()
   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)
   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
   --- End of inner exception stack trace ---
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
   at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)
 Process Name: w3wp
 Process ID: 4028

Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="System.ServiceModel 3.0.0.0" />
    <EventID Qualifiers="49154">3</EventID>
    <Level>2</Level>
    <Task>5</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2011-09-14T07:51:53.000000000Z" />
    <EventRecordID>18304</EventRecordID>
    <Channel>Application</Channel>
    <Computer>lw-it-exch01.londonwaste.co.uk</Computer>
    <Security UserID="S-1-5-18" />
  </System>
  <EventData>
    <Data>System.ServiceModel.ServiceHostingEnvironment+HostingManager/25879650</Data>
    <Data>System.ServiceModel.ServiceActivationException: The service '/ecp/Organize/AutomaticReplies.svc' cannot be activated due to an exception during compilation.  The exception message is: Security settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service.. ---&gt; System.NotSupportedException: Security settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service.
   at System.ServiceModel.Channels.HttpChannelListener.ApplyHostedContext(VirtualPathExtension virtualPathExtension, Boolean isMetadataListener)
   at System.ServiceModel.Channels.HttpTransportBindingElement.BuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener[TChannel]()
   at System.ServiceModel.Channels.MessageEncodingBindingElement.InternalBuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.WebMessageEncodingBindingElement.BuildChannelListener[TChannel](BindingContext context)
   at System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener[TChannel]()
   at System.ServiceModel.Channels.Binding.BuildChannelListener[TChannel](Uri listenUriBaseAddress, String listenUriRelativeAddress, ListenUriMode listenUriMode, BindingParameterCollection parameters)
   at System.ServiceModel.Description.DispatcherBuilder.MaybeCreateListener(Boolean actuallyCreate, Type[] supportedChannels, Binding binding, BindingParameterCollection parameters, Uri listenUriBaseAddress, String listenUriRelativeAddress, ListenUriMode listenUriMode, ServiceThrottle throttle, IChannelListener&amp; result, Boolean supportContextSession)
   at System.ServiceModel.Description.DispatcherBuilder.BuildChannelListener(StuffPerListenUriInfo stuff, ServiceHostBase serviceHost, Uri listenUri, ListenUriMode listenUriMode, Boolean supportContextSession, IChannelListener&amp; result)
   at System.ServiceModel.Description.DispatcherBuilder.InitializeServiceHost(ServiceDescription description, ServiceHostBase serviceHost)
   at System.ServiceModel.ServiceHostBase.InitializeRuntime()
   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)
   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
   --- End of inner exception stack trace ---
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
   at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)</Data>
    <Data>w3wp</Data>
    <Data>4028</Data>
  </EventData>
</Event>

Mody2579 edugeek link has pointed me in the right direction.  It was an IIS 7 authentication issue.

I've enabled anonymous access on the ECP application folder under default website and this has resolved the issue. Thanks for your help Experts.

iis 7 issue. ECP application needs annoymous access enabled