Re: PBL and rejects

[Viktor Dukhovni]

On Mon, Nov 14, 2022 at 04:08:28PM -0500, Alex wrote:

> I'm hoping I can ask this question here. Somehow the PBL considered the IP
> addresses given to us by our ISP (I can share this if needed) as ineligible
> to send email, resulting in any recipient domain that checks the PBL to
> reject our email, including every email sent to a Microsoft 365 domain.
> This is also despite having a rule to bypass spam filtering on the M365
> side with our own M365 domain - apparently that is not bypassed?

Generally, PBL listings are contributed by the responsible ISP, so it is
best to start with them.  Sometimes community nominations are added to
the PBL of address blocks that look substantially like dynamic consumer
IPs.  Perhaps that happened here.  Yes, PBL false-positives can (rarely)
happen.

-- 
Viktor.

PBL and rejects

[Alex]

Hi,

I'm hoping I can ask this question here. Somehow the PBL considered the IP
addresses given to us by our ISP (I can share this if needed) as ineligible
to send email, resulting in any recipient domain that checks the PBL to
reject our email, including every email sent to a Microsoft 365 domain.
This is also despite having a rule to bypass spam filtering on the M365
side with our own M365 domain - apparently that is not bypassed?

Does anyone know how this might happen? I've now delisted all of our IPs
successfully, and mail is again flowing, but it obviously resulted in a
pretty significant impact on our delivery.

I'm also trying to confirm I've configured my system properly to best
utilize RBLs.

smtpd_recipient_restrictions =
reject_non_fqdn_recipient,
reject_non_fqdn_sender,
reject_unlisted_recipient,
reject_unknown_recipient_domain,
permit_mynetworks,
reject_unauth_destination,
reject_rbl_client zen.spamhaus.org=127.0.0.[2..11]
reject_rhsbl_reverse_client dbl.spamhaus.org,
reject_rhsbl_sender dbl.spamhaus.org,
reject_rhsbl_helo dbl.spamhaus.org,
reject_rbl_client b.barracudacentral.org=127.0.0.2
 ...

Any suggestions greatly appreciated.

Thanks,
Alex