[Greylist-users] some comments on spamd

[Ronald Oussoren]

On 31-mei-2005, at 19:17, Graham Toal wrote:

> A final update on my saga of building a greylist server using spamd...
>
> It has been live in front of the University of Texas Pan American for
> two weeks now.  I am using greylisting plus a small list of  
> blacklisted
> IPs which I built myself by observing the traffic hitting the greylist
> and then checking each IP against other blacklists to make sure they
> were indeed bad networks.
>
> We have cut down incoming spam by 90%.  We now get one spam per good
> mail instead of 10 spams per good mail.  We reject over 80,000
> *connections* per day from spammers, and presumably far more actual
> spam deliveries than than (as many of the connections would have sent
> to every user on campus - 15,000+)

Do you, or anyone else, have any indication on the amount of false
positives with greylisting? I've disabled greylisting on a site because
several people complained that their mail didn't get through. It seems
that some mailers are confused by a 4xx result at an unexpected location
and drop that e-mail.

That is of course a bug in the sending MTA, but I find disappearing
e-mail highly disconcerning even if it is only a very, very tiny  
fraction
of all e-mail.

If it weren't for those disappearing e-mail I'd never disable  
greylisting,
we also got a 90+% decrease in the amount of incoming spam and e-mail
virusses.

Ronald

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