What does p=none actually do?

Nothing to the mail. It asks receivers to send you reports about what passes and fails, while delivering everything as usual. It is the right first step and the wrong permanent state.

Do I need both SPF and DKIM for DMARC?

DMARC passes if either SPF or DKIM passes and aligns with the From domain. Having both means a forwarded message that breaks SPF can still pass on DKIM.

Where do aggregate reports go?

To the mailto address in the rua tag, as XML attachments, roughly daily from each receiver. A reporting service turns them into something readable; raw XML is hard to use at scale.

DMARC checker

DMARC (Domain-based Message Authentication, Reporting and Conformance) is a DNS record that tells receivers what to do with mail claiming to be from your domain that fails SPF or DKIM, and where to send reports about it. This tool reads the record as a sentence, not a string of tags, and shows exactly what a receiver will do with mail that fails.

What this tool checks

It fetches the TXT record at _dmarc. plus the domain, checks there is exactly one, and parses every tag. The policy, subdomain policy, percentage and report addresses are folded into a one-sentence summary so you can confirm the record says what you meant.

Getting from none to reject

Publish p=none with a rua= address and wait two to four weeks of reports.
Fix every legitimate sender that fails: add it to SPF, or get it signing with DKIM on your domain.
Move to p=quarantine; pct=25, raise pct in steps, then p=reject.

DMARC at the handshake

Most gateways evaluate DMARC after the message is fully received. Spamjadoo evaluates SPF at MAIL FROM and, when the policy is reject and no aligned DKIM signature can rescue the message, refuses it during the session, so nothing is queued or stored.

Questions people ask

What does p=none actually do?: Nothing to the mail. It asks receivers to send you reports about what passes and fails, while delivering everything as usual. It is the right first step and the wrong permanent state.
Do I need both SPF and DKIM for DMARC?: DMARC passes if either SPF or DKIM passes and aligns with the From domain. Having both means a forwarded message that breaks SPF can still pass on DKIM.
Where do aggregate reports go?: To the mailto address in the rua tag, as XML attachments, roughly daily from each receiver. A reporting service turns them into something readable; raw XML is hard to use at scale.