Mail undelivered message.

Could not send to the below domain ID. Please sort out at the earliest.

Below message for your reference.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error.

 emcs@vsnl.net, ERROR_CODE :521, ERROR_CODE :5.7.1 Service unavailable; client [74.201.84.163] blocked using dnsbl.sorbs.net