Removing Server From a domain

I haope this is the correct place to post my question. If not, please advise.

I have a Redhat Linux 6 server that is part of our domain.

How do I remove this server from the domain it's in, and add it to another domain?

The server is not performing anything other than a smtp mail server. Thats it, not running nis,dns,,,etc....

Thanks in advance.