MX record error when sending to our mail server

Hi

We have been experiencing problems where certain people could not send mail to our server. It turned out the smtp greeting was wrong and needed to be changed from freestyle-rc.com to mail.freestyle-rc.com after doing this the same people now get the following error:

It appears that the DNS operator for freestyle-rc.com
> > has installed an invalid MX record with an IP address
> > instead of a domain name on the right hand side.

At the moment the mx record points to the ip address of our server. Do I need to change it or add a second record to point to mail.freestyle-rc.com ?

Thanks

Nick