the linux documentation project spam statz:

   56228   79.05%  DENIED_RDNS_MISSING
    6959    9.78%  DENIED_RDNS_RESOLVE
    3729    5.24%  ALLOWED
    1798    2.52%  DENIED_RBL_MATCH
--------------- Breakdown ---------------
   15178   94.82%  zen.spamhaus.org
     829    5.17%  bl.spamcop.net
-----------------------------------------
     871    1.22%  DENIED_IP_IN_CC_RDNS
     676    0.95%  DENIED_SENDER_NO_MX
     401    0.56%  DENIED_TOO_MANY_RECIPIENTS
     235    0.33%  ERROR
     173    0.24%  TIMEOUT
      52    0.07%  DENIED_RELAYING
       2    0.00%  DENIED_OTHER

---------------- Summary ----------------
Allowed:     3729    5.24%
Timeout:      173    0.24%
Errors :      235    0.33%
Denied :    66987   94.18%
Total  :    71124  100.00%