[FFmpeg-devel] mailman3 ffmpeg-devel-owner bounce mitigation

[Michael Niedermayer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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Hi all

I think ive finally found a way to fix the ffmpeg-devel-owners from
being unsubscribed/disabled due to spam bounces

Let me first explain what the problem is, then how we solved it.

The problem:
1. spam hits ffmpeg-devel-owners
2. our spam filters remove alot but not all spam
3. spam to ffmpeg-devel-owners is processed my mailman3
4. mailman3 forwards the spam to all the people on ffmpeg-devel-owners
5. some of this spam bounces because it is spam
6. the bounce is now indistingishable from a ffmpeg-devel subscriber
7. the bounce hits our server and is routed to mailman
8. mailman3 increases the bouce score for the address that bounced the spam (if theres a matching subscriber)
9. once the bouce score reaches the threshold the person has his subscription disabled
10. If you followed along, you will realize that mailman now disabled an account
   but that account was never involved in the bounce

mailman2 did not have this issue

What we tried:
1. Improve spam filtering, we did not run *-owner through all our
   spam filters, now we do, but its not enough.
   future plan here is to install rspamd

2. verp_probes = yes & probe_add_dsn: no
   This should prevent primary bounces from disabling accounts by
   having a final test message send (which should ideally not bounce
   as spam) sadly these seem to be able to bounce too

3. postfix
   we simply handle the ffmpeg-devel-owner in postfix now
   and now as mailman doesnt forward it, the return
   address is distinct from mailing list subscriber mail and thus any
   bounces from owners dont get counted as subscriber bounces.

ATM this is used only for ffmpeg-devel-owner,
i intend to enable the same thing for other mailing lists

what this also means, you can now again subscribe with the same mail
address to the list as used in ffmpeg-devel-owner without being
unsubscribed/disabled due to ffmpeg-devel-owner bounces.

Of course bounces from normal mailing list mail still can get your
account disabled.

thx

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.

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