On a Windows 2003 server....
After 2-3 years of working fine...all the stations on this network could no longer find www.mycompanysite.com
The site could be accessed from outside the network, however.
The people who wrote the site made some changes to DNS by adding:
Forward lookup zone:
Under that we added:
(same as parent folder) Mail Exchanger(Mx)  mail.mycompanysite.com
Mail Host [A] ip address
www Host [A] same ip address
After that, the problem went away. Before I get their explanation, I like input from this site.
Why would the above fix the problem?
I could see adding a forward lookup zone, but I am not sure why they added it the way they did.