the linux documentation project spam statz:

   52232   71.58%  DENIED_RDNS_MISSING
   10768   14.75%  DENIED_RDNS_RESOLVE
    3607    4.94%  ALLOWED
    2675    3.66%  DENIED_SENDER_NO_MX
    1992    2.72%  DENIED_RBL_MATCH
--------------- Breakdown ---------------
   11090   94.15%  zen.spamhaus.org
     688    5.84%  bl.spamcop.net
-----------------------------------------
    1087    1.48%  ERROR
     463    0.63%  DENIED_IP_IN_CC_RDNS
     100    0.13%  TIMEOUT
      27    0.03%  DENIED_TOO_MANY_RECIPIENTS
      19    0.02%  DENIED_RELAYING

---------------- Summary ----------------
Allowed:     3607    4.94%
Timeout:      100    0.13%
Errors :     1087    1.48%
Denied :    68176   93.43%
Total  :    72970  100.00%