All of a sudden, we are unable to access any of our website external to our network. They work perfectly fine within our network but when you try to access our websites including our OWA for our email which is hosted on a total different server we get a webpage is not available. I ran the DNS lookup tool from mxlookup on the domain cadca.org and the HTTP connect failed. The only modifications made to the network was the implementation of a new DNS server yesterday. I have checked the firewall settings and everything seems to be okay, I am starting to think it has something to do with DNS but don't know where to begin, can someone please point me in the right direction?
Below is our network
Sonicwall Model: TZ 210 wireless-N
VMware ESXi ver. 5.1
Windows Server 2012
Two domain controllers and both have DNS and DHCP server installed on them
Thanks in advance,