[CentOS] Postfix smtp_recipient_restrictions causing mail to fail

Hi All,

I'm currently playing with smtp_recipient restrictions to try and knock 
some of this spam on it's head. On my old debian server, I was using 
this and successfully filtering out at least 90% if not more of all spam 
emails which was great. I didn't even need spamassassin.

However, trying to do the same thing on my new CentOS based server isn't 
working. With the following enabled, nothing comes through from the 
outside world.

Can anybody see where I've gone wrong. I can't fathom why this would 
block all incoming emails from the web.

smtpd_recipient_restrictions =
     permit_mynetworks,
     permit_sasl_authenticated,
     reject_invalid_hostname,
     reject_non_fqdn_hostname,
     reject_non_fqdn_sender,
     reject_non_fqdn_recipient,
     reject_unknown_sender_domain,
     reject_unknown_recipient_domain,
     reject_rbl_client zen.spamhaus.org,
     permit

Thanks,

Kind regards,
Logan Moore