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? Would my ISP have listed them intentionally? 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. Any ideas greatly appreciated.
