'error while processing' message when setting up mail account

'error while processing' message when setting up mail account

i registered a new domain under zoho.com, but when i try to set up my email @mydomain.com, i keep getting this error message.  i go to control panel, mail administrators, mail accounts, create a new one and enter an address @mydomain.com.  then i get an error.  and i can't send or receive mail at my new domain/ address.  how do i fix?