External DNS resolution

We have been noticing that some of our none webhosting customers (internet service dial-up, dsl, wireless) that use our DNS servers are not resolving to the correct external websites.

We don't need help fixing the problem but since this is happening on 3 of our servers running DirectAdmin I wanted to know if anyone else was having a issue like this. Kind of strange...

What exactly do you mean by "are not resolving to the correct external websites" ? ... it's returning a value, but an incorrect one? It might be releated to the TTL for their ISP server.. or something like that.

John