This guide is for Exchange 2007 with ISA 2006. Go here for the BIS ISA Exchange 2003 solution. Ok firstly this guide assumes you know how to configure and publish secure websites through ISA. If you do not know how to do this then read up on it. Until you are confident you can set up and publish websites through ISA using web listeners there is not point continuing. This guide also assumes the ISA and Exchange servers are both in the same domain. If they are not there are additional steps you must take (explained at the end of the guide). The first thing we need to do is enable Forms Based Authentication (from now on called FBA) at the ISA box and disable FBA at the Exchange level (if enabled).
This article is for Microsoft Exchange 2003 and ISA 2004. Go here for the BIS, ISA and Exchange 2007 OWA Solution. This is caused by ISA 2004 being used to do the authentication and not the exchange box itself. I figured this out by investigating why Blackberry phones work perfectly well with an SBS 2003 server (which has ISA2004 and exchange 2003 installed on them) but not when they are installed on separate servers. It is all do to with Outlook forms and how the authentication is handled. When you use Outlook forms for authentication you are prompted with a nice Outlook splash page. At this point you type in your username and password to log in. This feature is enabled by default in a SBS 2003 installation but not with Exchange 2003 on a Windows Standard install. By default (on a win 2k3 std server) you will not get this splash page. Instead you get the grey pop up style box and have to log in this way instead. If you want to allow Outlook forms you must install and configure this component yourself on the exchange box. Now onto ISA.... Out the box ISA comes with Outlook forms