Emails from a certain sender or listserv are being blocked

Thank you for reaching out. 

We are writing to inform you that our domain enforces strict email authentication policies (including SPF, DKIM, and DMARC) to protect our organization and users from phishing, spoofing, and unauthorized message delivery. 

As part of these security measures, our email servers automatically reject unauthenticated messages. To ensure emails are successfully delivered to our domain in the future, please inform the sender that your email domain only accepts authenticated emails.

In the meantime, we have added their domain as an exception so that you can continue to receive email from them until they fix their systems.