Subdomain re-direct?

I am trying to redirect a subdomain but I keep getting the following error message:
“Can’t add domain: we set this sub-domain up automatically for you.”

I am trying to re-direct:
to another domain.

I assume Dreamhost has already setup the subdomain “mail” on all domains that are hosted, but is there anyway to get around this so I can use the “mail” subdomain?

I also tried using “email” subdomain re-direct and I couldn’t get it to work :frowning:
What am I doing wrong here?
Where are the redirects displayed in the Manage Domain’s portion of my DH Control Panel?

Thanks in advance,