First of all, I'm sorry to raise this sore point again but ..... I followed Tom's guide from http://www.isaserver.org/articles/2004pubowartm.html to publish my OWA site and all was working fine when I first installed it. I could access the OWA site from externally and internally with no problems whatsoever. Then I rebooted my ISA server (Can't remember why!) and now externally I can't connect. The error I get is 'Error Code: 500 Internal Server Error. The certificate chain was issued by an authority that is not trusted. (-2146893019)' I found a message http://www.adminlife.com/247reference/msgs/6/31593.aspx saying to 'Obtain the CA cert from the SBS2K3 server and install it in the ISA local machine store trusted root certs' - I have done this (but not from an SBS2K3, from my exchange server) and still no good. I have also re-exported and re-imported the cert, restarted the ISA server again and still I get the same error. In the mean time, if I connect via VPN or connect from the local network it works fine. I searched for any other possible reasons using google and M$ knowledgebase but still can't find the fault. Does anyone know what I have done wrong and what I can do to fix it? Thanks ..Spence