I see a good number of questions on whether or not you can use a machine account to authenticate with the ISA firewall. My thoughts on this issue in the past is that this is not possible, but a recent post on the ISA Server Team Blog may have me rethink my position on this. However, it’s unclear from the post on the blog whether you can actually use this for user applications, since they state that it’s only useful for applications running under the Local System or Network Service account.
I’ll have to test this to see how it might work in practice. Maybe you can figure it out. Find out by checking the blog post at: https://blogs.technet.com/isablog/archive/2006/06/29/439329.aspx
Thomas W Shinder, M.D.
MVP -- ISA Firewalls