Hi Himanshu,
As your application is hosted on a GAE Flexible environment instance (since redirected URL includes *.appspot-preview.com), custom domains need to be whitelisted as mentioned in this Before you Begin section <https://cloud.google.com/appengine/docs/flexible/nodejs/using-custom-domains-and-ssl#before_you_begin>. In the third point, it is possible to whitelist the domains by filling out this Google contact form <https://support.google.com/cloud/contact/gae_flex_custom_domain>. However, as this form is currently unavailable, you will be contacted by email shortly to provide additional information regarding your project. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to google-appengine@googlegroups.com. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/bc798d13-f334-433d-87d7-8c0f06b611e9%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
