the linux documentation project spam statz:

   40139   82.42%  DENIED_RDNS_MISSING
    3652    7.49%  DENIED_RDNS_RESOLVE
    2268    4.65%  ALLOWED
    1480    3.03%  DENIED_RBL_MATCH
--------------- Breakdown ---------------
   47978   98.70%  zen.spamhaus.org
     631    1.29%  bl.spamcop.net
-----------------------------------------
     526    1.08%  ERROR
     444    0.91%  DENIED_IP_IN_CC_RDNS
      98    0.20%  TIMEOUT
      73    0.14%  DENIED_SENDER_NO_MX
      11    0.02%  DENIED_RELAYING
       8    0.01%  DENIED_TOO_MANY_RECIPIENTS

---------------- Summary ----------------
Allowed:     2268    4.65%
Timeout:       98    0.20%
Errors :      526    1.08%
Denied :    45807   94.06%
Total  :    48699  100.00%