This might not even be related to the firewall but I decided to post anyway. Between our users and the internet there is a router, firewall and switches. So I can only think the firewall could be causing this:
User cannot login to a webmail site (webmail.windstream.net). They get the error (Access to Windstream Webmail is denied. Error 100 ). I tested from different machines and verified it. I have an email with windstream so, I tested connecting to other 2 diferent ISP's an sure enough I am able to log in just fine.
Would you guys give me some ideas about where to look. As far was we know nothing has changed in the firewall config. It started happening since last Friday