dav.webmail.bell.net has no CNAME records.
Question and response
Question
dig dav.webmail.bell.net. NS
Answer
The response has no answer records.
Authority
bell.net. 900 SOA mtl02vnszs08.srvr.bell.ca. trademarks.bell.ca. 6530 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0