Prove that your problem really is a DNS problem.

You've come to this page because you've asked a question similar to the following:

• I have a problem with my mail system. How do I fix my DNS services?

• I have a problem with my web browser. How do I fix my DNS services?

This is the Frequently Given Answer to such questions.

Prove that your problem actually is a DNS problem. So far, you haven't. Since you haven't, you have no grounds for choosing to attempt to fix your problem, whatever it actually is, by fiddling with your DNS services. If your problem lies elsewhere, it's a waste of our time and money to help you to fiddle with your DNS services. So prove to us that you won't be wasting our time and money.

Use the right tools for the job

Use DNS diagnosis tools to perform DNS lookups. Follow the standard litany for problem reporting and explain to us what results you expect to see and why the results that you actually see are wrong.

If the results of the DNS lookups are not wrong, then you don't have a DNS problem.

Read the error messages from your mail system

The error messages from your mail system will tell you what the problem is, and whether it is actually related to the DNS at all. (Furthermore: If you want us to help you with your mail system problem then show us the error messages. Don't expect everyone's clairvoyance to be working today.)

A web browser is not a DNS diagnosis tool

A web browser is not an effective DNS diagnostic tool, no matter how pretty its error message displays may be. Web browsers do all sorts of things in addition to DNS lookups when loading and displaying web pages.

And, unfortunately, some web browsers are exceedingly bad at explaining what the actual problem that they have encountered is in their error messages. They "dumb down" the error message to the point where it contains no useful information whatever.

The web browsing problem that you have could be any of a vast number of things, most of which are entirely unrelated to DNS service. It could be a problem with:

• your web browser's private "search path" mechanism (that turns domain names such as "example" into "www.example.com", for example);
• your DNS Client's separate "search path" mechanism (that turns non-fully-qualified domain names such as "www.example.com" into fully-qualified domain names such as "www.example.com.example.net.", for example — Yes, that really does happen.);
• your web browser's "send this string to a search engine" mechanism, if it has one;
• the search engine that your web browser uses;
• one of the "plug-ins" that you have installed in your web browser, doing things under the covers with the string that you entered;
• your web browser's own cache of web objects;
• your proxy HTTP server, if you are using one;
• an interception proxy HTTP server run by your ISP, if your ISP is foolish enough to employ such a bad idea;
• your web browser's proxy auto-configuration mechanism;
• your IP connectivity (routing, hop counts, firewalls, NAT, &c.) to the rest of Internet;
• your IP connectivity (routing, hop counts, firewalls, NAT, &c.) to the relevant HTTP server;
  or
• the actual content HTTP service itself.

Before blundering about, randomly prodding things that may not have anything at all to do with your problem, narrow the locus of your problem down.