DMARC failure will cause whitelisting to be ignored. This is on purpose, since the spammer may be spoofing a From address. There were two recent problems in the past week or so which Fastmail staff discovered after being informed of some spam filing problems:
- Address book whitelisting was disabled for some messages, even though they passed the DMARC test. This failure was erratic, and I believe it was fixed a few days ago.
- Some messages from domains which are not publishing any DMARC records were classified as failing DMARC authentication. I think this will be fixed within the next day or two.
So wait another day or two and see if you see see DMARC failures. Some forwarding services may break DMARC if they corrupt the DKIM signature or message contents, and they will probably break SPF. Either DKIM or SPF must pass for DMARC to pass.
Bill