Mail doesn't work on addon domain

[RuleMaker]

When I use my original domain name (keepitfit.heliohost.org) to access the php script that sends the mail it gets delivered but if I use the addon domain (keepitfit.co.cc) it doesn't.

I probably misconfigured the MX entries, currently my addon domain is configured to use local mail exchanger with destination keepitfit.co.cc and priority 0.

 

Thanks in advance.

[fantasyzer]

In order to help you we need a little bit more details. What is the error message you are receiving from your mail server or the one that you are trying to mail to? What method of sending emails do you use?