[computer-go] repeat postings

[Heikki Levanto]

On Mon, Aug 27, 2007 at 04:22:08PM -0400, Don Dailey wrote:
>
> On Mon, 2007-08-27 at 21:35 +0200, Heikki Levanto wrote:
> > Some mail servers are starting to use greylisting, which
> > intentionally delays mails that have sender-recipient pairs they
> > have not seen before - this fouls a lot of spamming programs (I do
> > that at my place of work).
> 
> How does this foul spamming programs?   Does it prevent a spammer from
> sending out a lot of email or just delay the receiving of it?

Many spam programs are not fully capable mail programs, and have not
implemented any sort of retry mechanism. I was sceptical about it too,
until I installed it. Perhaps the spammers are catching up now, but a
year ago, it dropped more than 75% of incoming spam - enough that our
mail server could afford to do proper filtering on the rest.

And it is not like all mail gets delayed, the filter keeps a hash of
sender-address, receiver-address, and connecting IP-address. If it has
accepted one mail with a matching hash in the past 45 days, no delays
are imposed. 


But this is getting off topic.

  - Heikki

-- 
Heikki Levanto   "In Murphy We Turst"     heikki (at) lsd (dot) dk