I recently faced a weird issue when Quad 9 DNS Servers ( were stopping login to Office 365 Portal or Adobe from India.

What is Quad 9 – The Global Cyber Alliance in partnership with IBM ECM and Packet Clearing recently launched this free dns service to combat botnets, phishing attacks, and other known bad devices. This service get it’s feed from different known sources. Organization can point their forwarders to to use it’s free service.

Error message

Login to portal.office.com was stuck on login screen and adobe was showing distorted website. I did fiddler trace and saw 502 error code and it was thrown for a particular endpoint. it was causing issue with adobe’s websites as well. Hence we were sure that this was Quad 9 ( which was causing the issue.

Issue with Accesing portal.office.com

  • 502 Error Code 


  • Error of highlighted 502 HTTP Error

Fiddler Logs1


Changing forwarder to google dns ( fixed the issue, but we need to still talk to quad 9 to fix the issue at their end.

You can use this article as a reference point for your troubleshooting and make sure you don’t forget the DNS can also cause such issue.s