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From Reindl Harald <h.rei...@thelounge.net>
Subject Re: Uptick in spam
Date Sat, 28 Mar 2015 11:13:58 GMT

Am 28.03.2015 um 12:04 schrieb David Jones:
> I know that but I choose to use the "traditional" method in the Postfix
> smtpd_recipient_restrictions so I can specify the order.  I have such a
> high volume of mail for more than 100,000 mailboxes, I want to check
> in a specific order using my local rbldnsd feed to prevent abuse of other
> RBLs further down the list

the problem with this approach is that with each RBL you raise the 
false-positive rates extremely, until now i did not see any RBL without 
FP be it Zen, Barracuda or Spamcop

most caused by fools reporting mails they subsribed to as spam instead 
unsubscribe, frankly i got recently even two AOL feedback loops 
including the original message where customers of our ustomers reported 
there monthly e-bill including the bill itself as spam

the same for digest services (Pyzor, Razor, IXHASH)

with postscreen-scoring you can avoid that completly by not giving any 
RBL the power to reject a mail while at the same time add a few very 
false positive prones with a low score - the result is you block much 
more spam on RBL level with way less complaints and given that 
"postscreen_dnsbl_ttl = 10m" even applies to RBLs with a TTL auf just a 
few seconds (Spamhaus) your total dns queries could go down

another thing is performance: "smtpd_recipient_restrictions" is 
sequential while postscreen asks all RBLs parallel, if one or more have 
a timeout it don't block, they are just not taken into account at that 
moment, when you have enough RBL's the result is still good



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