Mail server

hi everybody,
I am using opensuse 11.3 as a server configured by YaST (DNS , DHCP , NFS , LDAP , HTTP , NTP ) and everything (indeed everything) works perfect. But (there is always a BUT) , when i tried to configure the Mail Server (Advanced Settings) something went wrong and was not functional. I was getting a message “cannot write main domain name”.
Yes,the ldap support on DNS is active and everything else is functional.

Any guidance ?
thnx
dim - Greece