postgrey

[Ethan Blanton]

Luke Schierer spake unto us the following wisdom:
> More because I'm unable to figure out why it would ever delay somedthing
> more than 300 seconds than because I'm convinced with your arguments in
> theory, I have turned it off.

This is something which was confusing people on #pidgin, as well, so
let me elucidate ...

You cannot control the length of the delay imposed by the graylisting,
all you can do is define a *minimum*.  The actual delay is controlled
by the remote server, and is the amount of time it takes to decide to
retry.  As you are essentially telling the remote server "I am
overloaded, please try again later", any *good* mail server is going
to wait some nontrivial period of time before trying again, preferably
with some sort of exponential backoff.  Five minutes (300 seconds) is
not an unusual *initial* retry period.

> I've been running spamprobe on my mail here, with a cron job teaching it
> on the spam it misses (all of it) since we set up pidgin.im.
> 
> I now have over 1000 pieces of spam it has missed, some of which
> spamassassin has caught.  All of these reached us via SF, and so
> bypassed the greylisting.  On schierer.org, I have gotten spamprobe to
> catch some, but far from all of my spam and only with the combination of
> spamprobe and spamassisin *both* scanning my mail (spamassasin filtering
> after spamprobe and filtering into the directory spamprobe learns from),
> am I catching a decent percentage of my spam.

Interesting, since you seem to be retraining spamprobe on the spams it
misses.  I use spamprobe on several accounts which receive hundreds of
spams per day (one of them, I think about 500), and I leak no more
than a handful a week.

> At accelerated servers, I get a hand ful of spams per week, down from
> spam levels equivalent to my SF account, since installing postgrey.  I
> see this as proof that it does better for preventing spam than any
> filter I've met.

I'm not saying it doesn't filter spam -- I'm saying it is a
technically poor idea.  Executing first time criminal offenders will
probably reduce crime, too, but we shouldn't do it.  Postgrey is an
example of overreaction to a problem.

Ethan

-- 
The laws that forbid the carrying of arms are laws [that have no remedy
for evils].  They disarm only those who are neither inclined nor
determined to commit crimes.
		-- Cesare Beccaria, "On Crimes and Punishments", 1764
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