this two servers are well know to work well togheter and they are famous to report really few false positive.

The SCBL is aggressive and often errs on the side of blocking mail.

If you want to lose legitimate emails at some point in time then you've done the right thing - adding an RBL to your mail server to immediately reject email.

Don't do this. You're relying on the owner/organisation of each RBL to be fairly cautious when blocking IPs. Maybe Facebook was a bit too spammy for spamcop and they legitimately blocked them for a reason - however you obviously don't consider Facebook to be an evil spammer (neither do I). However if your mail server is set to blindly trust those RBLs, you'll always get false positives.

Use a spam scanning filter which uses RBLs to filter email accordingly and remove them from Postfix. Try using amavisd-new with SpamAssassin enabled - by default it should come up with a list of RBLs it checks, you can always edit these if you want a different set with alternative scores if you trust a specific RBL more.

This way an email will get a higher spam score if the source of the message is from a blacklisted IP, but won't be immediately rejected. It gives SpamAssassin a chance to evaluate a message and see if the message is genuine spam if other RBLs say so, if all the other various rules make it look like spam - or if it's just a single RBL which is being overzealous in blocking certain IPs.

Don't use RBLs directly in your mail server unless you absolutely trust them.

… so I'm asking for a trusty RBL …

warn_if_reject
Change the meaning of the next restriction, so that it logs a warning instead of rejecting a request (look for logfile records that contain "reject_warning"). This is useful for testing new restrictions in a "live" environment without risking unnecessary loss of mail.

If you must RBL directly, just use zen.spamhaus.org -- it's conservative enough to not cause too many problems.

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,
   reject_unauth_destination