Optimize postfix configuration
install/tpl/*_postfix.conf.master
Right now (v3.1.5) this is the order of checks for "smtpd_recipient_restrictions":
permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, check_recipient_access mysql:{config_dir}/mysql-virtual_recipient.cf {rbl_list} {greylisting}
But SQL requests are expensive and resource consuming. Isn't better to move the RBL checks before check_recipient_access? This way if the sender IP is blacklisted then we save extra database checks.