Issues allowing yahoo.com in ISA 2006

There was a simple requirement for one of my clients, to configure firewall to protect from internet and also restricting users to access some external sites. So the requirement was to allow only google.com, some of the external mail sites and restrict all other sites. Installed and configured ISA 2006. This can be achieved by creating Domain Name sets and Access Rule for each site, allowing google.com, gmail.com, rediff.com and yahoo.com. Have created the Access Rules for the same. However yahoo.com was not accessible properly. When accessed I got the home page of yahoo.com but the font was different and all images in the home page were not loaded showing many red X marks.

Have rechecked the configuration of ISA and nothing was found. Unlike other mail sites, Yahoo has a different URL for loading images. I have checked it in the google and found a separate URL for yahoo images. Adding the image URL *.yimg.com in the allowed Access Rule, yahoo.com is accessible normally with the proper images and font.

This problem doesn’t occur when you allow all the external sites, as yimg.com will be allowed by default.