Sorry, I was stuck in different activities hence i am unable to reply to your message.
When user trying to access test1.abc.com it is should redirect to xyz.abc.com.
Then, user will fill survey for which is made by sharepoint once user submit the survey. then sharepoint redirect to test1.abc.com. if the referrer match with xyz.abc.com for test1.abc.com should not redirect i mean should not causing the issue.