Go to http://hda/setup?sub=2&tab=network
- * Add a new alias - * Fill in alias: the service you want to reach on your external URL, but only the first part. "mail" or "www" - * In the Ip-adress field fill in the external IP-adress for your external URL. (Four the four sets of numbers with dots inbetween)
That would do the trick (at least it did for me)