So i followed the Umbraco guide to making a custom 404 handler as I run multiple domains on my Umbraco instance.

Web.Config Entries (Dev and Production):

<!-- <add key="404Domains" value="xyz.umbraco.local,3315;zyx.umbraco.com,3316" /> --> 
<add key="404Domains" value="www.xyz.com,3315;www.zyx.com,3316" />

404handlers.config:

<?xml version="1.0" encoding="utf-8" ?>
<NotFoundHandlers>
<notFound assembly="umbraco" type="SearchForAlias" />
<notFound assembly="umbraco" type="SearchForTemplate"/>
<notFound assembly="umbraco" type="SearchForProfile"/>
<notFound assembly="umbraco" type="handle404"/>
<notFound assembly="UmbracoUS1" namespace="UmbracoUS1.Handler" type="URLNotFound" />
</NotFoundHandlers>

404handler.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using umbraco.interfaces;
using System.Configuration;

namespace UmbracoUS1.Handler
{
    public class URLNotFound: INotFoundHandler
    {
        private int redirectId;
        private string[] domains
        {
            get
            {
                try
                {
                    return ConfigurationManager.AppSettings["404Domains"].Split(';');
                }
                catch
                {
                    return null;
                }
            }
        }
        bool doReturn = false;

        public bool Execute(string url)
        {
            var server = HttpContext.Current.Request.ServerVariables["SERVER_NAME"].ToLower();

            foreach (string domain in domains)
            {
                if (domain.Contains(server))
                {
                    redirectId = Convert.ToInt32(domain.Split(',')[1]);
                    doReturn = true;
                    break;
                }
            }

            return doReturn;
        }

        public bool CacheUrl { get { return false; } }
        public int redirectID { get { return redirectId; } }
    }
}

The code works fine in development (VS) and my local deployment, but when I put this code into production the 404 is not caught by the handler.

My local deployment that is working is using the full version of IIS 7 and not express. I do not see anything in the trace logs.

Has anyone experience the same issue? The only thing that is different from dev to production is the 404Domains key in the web config.

I have tested the foreach logic in my master templates and the server value is being matched with the domain value coming from the Web.Config appSetting.

Is there an IIS setting I am missing?

Slowly pulling my hair out!

Many thanks

Phillip