handling long-term unreachable addresses/domains

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handling long-term unreachable addresses/domains

Matus UHLAR - fantomas
Hello,

on a few mail servers/gateways, we receive mail from domains that are
unreachable for mail delivery on a long-term basis.

besides spammers, there are companies that send mail from domains which
don't have MX records, and A records point to servers without mail service
running.

I would like to detect this kind of domains and block them.
Ideally, not immediately, but when e.g. domain is inaccessible for a given
time, e.g. when mail starts being returned.

Is something similar possible now?


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Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
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Re: handling long-term unreachable addresses/domains

Matus UHLAR - fantomas
On 09.01.20 17:09, Matus UHLAR - fantomas wrote:

>on a few mail servers/gateways, we receive mail from domains that are
>unreachable for mail delivery on a long-term basis.
>
>besides spammers, there are companies that send mail from domains which
>don't have MX records, and A records point to servers without mail service
>running.
>
>I would like to detect this kind of domains and block them.
>Ideally, not immediately, but when e.g. domain is inaccessible for a given
>time, e.g. when mail starts being returned.
>
>Is something similar possible now?

I was thinking about something very similar that address verification does:
- applied on domains, not individual addresses
- applied softly, without explicit verification checks

This would require database of mail domains, and if mail to any domain is
unreachable for interval longer than maximal_queue_lifetime, mail for/from
that domain would get rejected and or deferred.

Until then, mail would be accepted as reachable.

Any idea if this could be implemented?

--
Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
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Re: handling long-term unreachable addresses/domains

Wietse Venema
Matus UHLAR - fantomas:

> I was thinking about something very similar that address verification does:
> - applied on domains, not individual addresses
> - applied softly, without explicit verification checks
>
> This would require database of mail domains, and if mail to any domain is
> unreachable for interval longer than maximal_queue_lifetime, mail for/from
> that domain would get rejected and or deferred.
>
> Until then, mail would be accepted as reachable.
>
> Any idea if this could be implemented?

Use check_policy_service, reading from a domain status database,
populated with a "postqueue -j" cronjob that looks at the arrival_time
and delay_reason fields. Alternatively the same info could be mined
from logfile records. Again, a cronjob is good enough.

        Wietse