exchange.maa.sify.net has no CNAME records.
Question and response
Question
dig exchange.maa.sify.net. NS
Answer
The response has no answer records.
Authority
maa.sify.net. 4660 SOA syslog.maa.sify.net. hostmaster.sify.net. 2000101980 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0