I believe the problem is more with the mobile device - I'm not sure there's any way you can change the ports that uses. Otherwise there would be no problem changing the ports on the default website. Most problems I've experienced with Activesync in the past have been related to authentication - you should set it to only use "Basic Authentication" to start with. It can also be quite touchy about how you supply the user credentials, even if you have supplied the default domain setting in IIS - I've found that with IE it often likes the username in the format username@domain.local whereas in Mobile Activesync it prefers the domain to be set separately as just DOMAIN

Thanks for the quick response.  However trying different ways of representing the username has not seemed to make a difference.  When trying https://servername:4433/oma (i have changed the default web site to use 4433 instead of 443, and OWA works fine this way).  I am prompted for usename and password.  After entering I get the classic   A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator message.  I do have the following written into the App. Log on the Exchange Server.  
An unknown error occurred while processing the current request:
Message: Object reference not set to an instance of an object.
Source: Microsoft.Exchange.OMA.Preferencing
Stack trace:
   at Microsoft.Exchange.OMA.Preferencing.AdUserObject.FindUserViaCreds(NetworkCredential creds, WindowsIdentity identity)
   at Microsoft.Exchange.OMA.Preferencing.OmaUserInfo.ClearCache()
   at Microsoft.Exchange.OMA.Preferencing.OmaUserInfo..ctor(NetworkCredential creds, WindowsIdentity identity)
   at Microsoft.Exchange.OMA.Preferencing.OmaUserInfo..ctor(NetworkCredential creds)

Message: Exception has been thrown by the target of an invocation.
Source: mscorlib
Stack trace:
   at System.Reflection.RuntimeConstructorInfo.InternalInvoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean isBinderDefault)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)

Message: Exception of type Microsoft.Exchange.OMA.DataProviderInterface.ProviderException was thrown.
EventMessage:
UserMessage: A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator.
Source: Microsoft.Exchange.OMA.UserInterface
Stack trace:
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)
   at System.Web.SessionState.SessionStateModule.RaiseOnStart(EventArgs e)
   at System.Web.SessionState.SessionStateModule.CompleteAcquireState()
   at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData)
   at System.Web.AsyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Is this a configuration issue or is it becuase I am usung non-standard Ports.

I must type quicker.

The non standard port will break things. Put it back to the default.
Make sure that you don't have require SSL enabled on either /exchange or /oma

Simon.

Oh I am well aware of article 817379.  Can probally do it by memory now. :)  I was afraid that it might be a port issue.  There is no FBA configured and I have many, many times ensured that /exchange and all do not have SSL required (although I do have a home grown certificate installed - boss needs to have OMA work with SSL. :(

Going to try 817379 one more time with the tips from your web site.  I had not removed the certificate form the Default web Site before tyring 817370 before.

Thanks

OK, thanks for all the advice.  We have multilple IP addresses available to us here.  I am going to move the OMA/AS/OWA to a differnet IP address that I can use port 80 and 443 with.  However I will not be able to do that until the weekends.

Thanks again.