Is the internet ready for DMARC with p=reject?
No. DMARC is an email policy that builds on DKIM and SPF to provide a way for email senders to declare: "All email from this domain comes from this set of servers (SPF) , and is signed using these public keys (DKIM) ." It's nice and well that we are finally able to do that, but DMARC comes with 3 modes of operation: p=reject, p=quarantine, and p=none. These modes suggest what a recipient should do if an incoming email doesn't match the sender domain's DMARC criteria, either due to signature failure (DKIM) or incorrect sending server (SPF). The default mode, p=none, boils down to "do whatever, maybe this helps you guess if the email is spam". The mode p=quarantine treats the email as spam, and p=reject is supposed to cause the message to be rejected at the point of ESMTP delivery. Well, I tried p=reject, and it kinda works. Mostly. Except in the following situations: If you send to any mailing lists from your domain. Your messages may be DKIM