[Gross] Spammers adapt

[Eino Tuominen]

Hi,

I just noticed that our match rate is much higher now than it has been 
before. I did some log analysis and found lots of patterns like this:

Feb 28 19:39:32 smtp01 grossd: [ID 702911 mail.info] #a78: greylist: 
190.48.141.76 jr.tolerd at kecoindustries.com our-user
Feb 28 19:39:36 smtp01 grossd: [ID 702911 mail.info] #a79: greylist: 
190.48.141.76 jr.tolerd at kecoindustries.com our-user
Feb 28 19:39:47 smtp01 grossd: [ID 702911 mail.info] #a24: match: 
190.48.141.76 jr.tolerd at kecoindustries.com our-user

That is, retries go now beyond 10 seconds delay I've been using. I just 
resized our filter_bits to 26 and set grey_delay=120.

Next I've decided to implement weights on checks and implement that 
block_threshold so grossd can reject obvious spammers with permanent 
errors. I've been pondering this kind of setup:

dnsbl = bl.spamcop.net;2
dnsbl = dnsbl.njabl.org;1
dnsbl = dnsbl.sorbs.net;1
dnsbl = zen.spamhaus.org;3
dnsbl = rbl-plus.mail-abuse.org;3
block_threshold = 4

That is, no one match will lead to a permanent rejection, but two will 
be enough if one of them is highly trusted (spamhaus or rbl-plus).

-- 
   Eino Tuominen