Den 12.03.2026 20:31, skrev Bill Cole via Postfix-users:
On 2026-03-10 at 20:46:54 UTC-0400 (Wed, 11 Mar 2026 13:46:54 +1300)
Tim Harman via Postfix-users <[email protected]>
is rumored to have said:
On 11/03/2026 8:50 am, Fred Morris via Postfix-users wrote:
On Tue, 10 Mar 2026, Gary R. Schmidt via Postfix-users wrote:
[...]
Turn on postscreen and add fail2ban.
I learnt (I forget how, that's the problem) that if you're using
rspamd, you shouldn't do anything else like fail2ban or postscreen,
so that rspamd can learn _all_ mail. If you reject it as spam before
it even gets to rspamd, then rspamd ends up learning mostly ham and
very little spam, so things like the IP Reputation and
bayes/neuralnet training suffer because they don't see enough of both
sides.
I guess I can see some value in fail2banning an IP that rspand has
flagged as spam the last 20 times, to stop the CPU overhead of rspamd
having to check it a 21st time.
But that is learnt wisdom correct, or am I holding onto a belief
that's not in fact true?
I have not tested it rigorously in MANY years but when I wanted to be
sure, I found that switching off pre-SpamAssassin rejections did not
really improve the performance of the SA Bayesian "learning"
subsystem. Much more mail was hitting SpamAssassin but much of the
mail that was being rejected and learned as spam was a sort of garbage
that we never saw with the pre-SpamAssassin rejections active.
TL;DR: (filtered through my own experience)
Classes of mail, with intrinsically distinct fingerprints (as seen by
e.g. bayes)
-----
1 wanted
2 solicitation from real business contacts
3 manually posted spam from freemail
4 bots
-------
If number 4 is taken out by POSTSCREEN there is not much lost in the
learning for your bayes filters.
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