[Exim] RBL logs

I'm using exim 3.35 on debian stable. I hope to minimise spam by using
RBL's but I have no means of telling how effective it is.

This is in my conf:
rbl_domains = blackholes.mail-abuse.org/reject : \
         dialups.mail-abuse.org/reject : \
         relays.mail-abuse.org/warn
rbl_hosts = !x.y.a.0/24:!x.y.b.0/24:!x.y.c.0/24:0.0.0.0/0

recipients_reject_except = postmaster@???
rbl_log_headers = true
rbl_log_rcpt_count = true
log_refused_recipients = true

Does this seem ok? (ie. x.y.a.*, x.y.b.* and x.y.c.* are supposed to be
local networks and mail from them should not be checked against the RBL.)
What should I look for in the log files?

Regards,
Alex