Your QSA or acquiring bank asks how you “detect and protect personnel against phishing attacks” under PCI DSS requirement 5.4.1 — and your email domain has no DMARC, or sits at p=none.
PCI DSS v4.0's requirement 5.4.1 became mandatory on 31 March 2025: entities handling cardholder data must have processes and automated mechanisms against phishing. The requirement text doesn't name specific technologies, but the PCI SSC's own guidance lists DMARC, SPF and DKIM as example anti-spoofing controls — and assessors routinely expect them on domains involved in cardholder communications.
p=none record is monitoring, not the “protection” the requirement describes.DNS changes propagate within minutes to 48 hours. Mailbox providers pick up the new records on their next check — most senders see bounces stop within a day of correct configuration.
Formal enforcement targets bulk senders, but partial authentication already costs you inbox placement at every volume — and spoofing protection matters regardless of how much you send.
Hosting support can add DNS records for you, but they don't know which services send as your domain. You (or a monitoring tool reading your DMARC reports) have to provide that list — that's the actual hard part.