ding! The 5 seconds is probably due to DNS timeout in one of the RBL servers.
Len
My RBLs below:
reject_rbl_client blackholes.easynet.nl,
reject_rbl_client list.dsbl.org,
reject_rbl_client opm.blitzed.org,
reject_rbl_client relays.ordb.org,
reject_rbl_client sbl.spamhaus.org,
