the linux documentation project spam statz:

   47908   70.50%  DENIED_RDNS_MISSING
    6497    9.56%  DENIED_RDNS_RESOLVE
    3854    5.67%  ERROR
    3826    5.63%  ALLOWED
    3120    4.59%  DENIED_IP_IN_CC_RDNS
    2365    3.48%  DENIED_RBL_MATCH
--------------- Breakdown ---------------
   13545   88.95%  zen.spamhaus.org
    1682   11.04%  bl.spamcop.net
-----------------------------------------
     180    0.26%  DENIED_SENDER_NO_MX
     127    0.18%  DENIED_TOO_MANY_RECIPIENTS
      48    0.07%  TIMEOUT
      23    0.03%  DENIED_RELAYING

---------------- Summary ----------------
Allowed:     3826    5.63%
Timeout:       48    0.07%
Errors :     3854    5.67%
Denied :    60220   88.62%
Total  :    67948  100.00%