Freehostia - BigCartel & Zoho integration

Freehostia - BigCartel & Zoho integration

I purchased my domain at Freehostia, then setup an online store with BigCartel.  I created a CNAME record in Freehostia to point to BigCartel and it worked.  I am trying to point the MX records to Zoho Mail so that I can have branded email too.

Freehostia is telling me that since I created the BigCartel CNAME record, that I can't point the MX somewhere else.

Is this true, or not?

Thanks for any help.