I can try to explain, have a customer that is on a 2012 Active Directory Domain. They are having trouble submitting a form from this one website. Computers that are not part of the Domain have no issues, neither does anyone else outside the network. Things I have tried are removing Anti-Virus software, changing the DNS they are pointed to. Packet captures from firewall show nothing blocked. Have tried the sites from other Domains with no problem. Connect to there network with a computer that has never been on the Domain and it works fine.
Very confusing, not sure what is happening.