Hi All, We are having an Internet data centre kind of a web application that we need to host. We have back-to-back DMZ scenario with IIS in the DMZ. AD/DNS, Exchange 2000 & some other MS.NET servers are in the internal network behind the second firewall (Internal ISA- ISA1). AD and DNS are on the same machine. ISA1 >> IIS >> ISA2 >> AD/DNS, Exchange2000, SQL, etc We have configured IIS to join the internal domain. This is needed by the application as user needs to be authenticated against the AD which is in the internal network. I know this is not a recommended option from the security perspective but, I can?t think of any other option. Any ideas on this?.. But, the real issue at this time is not IIS, we have Exchange 2000 that needs to send & receive emails to the internet cloud. Can someone direct me on how to go about this? I have read both the articles in the Learning Zone by Thomas Shinder ?ISA Server SMTP Server Support? and ?Publishing a Mail Server with ISA Server?. I do not know which one is applicable. For an external ISA (ISA1) we will use ISP?s DNS. For the internal domain we have DNS on the AD machine. IIS also has a secondary DNS (replicated from the internal DNS) Any help in this regard is much appreciated, thanks for reading. Thanks, Rhys