I finally got through to Docker Hub via the company proxy. To ease up things for others having strict proxy policy, below the list of urls needed to whitelist to get through:
dseasb33srnrn.cloudfront.net
auth.docker.io
elb-registry.us-east-1.aws.dckr.io.
us-east-1-elbregis-10fucsvj1tcgy-133821800.us-east-1.elb.amazonaws.com
registry-1.docker.io
registry-origin.docker.io
index.docker.io
elb-io.us-east-1.aws.dckr.io
us-east-1-elbio-rm5bon1qaeo4-623296237.us-east-1.elb.amazonaws.com
Please note that the list is site specific, depending on your location. This worked from North Europe. Also the mirrors may change from time to time… still looking for up-to-date list of mirrors…