I have had this particular DNS server set up for quite a few years now. Recently, I got some complaints that we could not email one particular external domain. I tried an nslookup on this domain and it will not resolve. I then tried hitting their website and obviously that doesn't work. I went to the DNStools website and tried to resolve the domain name from there. It worked. I have no problem with any other websites or email addresses that I am aware of. Any suggestions on how to resolve this issue?