How can DMARC prevent domain spoofing?

Imagine someone sends an email that looks like it's from captain@deepcurrent.io, your domain, but you never sent it. That's domain spoofing, and it's a real problem because the receiving inbox has no way to tell the difference without authentication in place.

Domain spoofing works by forging the "From" address to impersonate a trusted sender. DMARC shuts that down by combining two checks: SPF (which confirms the sending server is allowed to send for your domain) and DKIM (which confirms the message carries a valid cryptographic signature from your domain). If a spoofed message fails both of those checks, DMARC tells the receiving server what to do about it.

That's the key word: tells. DMARC doesn't just detect failures. It gives receiving servers explicit instructions through your policy. A policy of p=quarantine sends the suspicious email to the spam folder. A policy of p=reject blocks it from being delivered at all. Either way, the spoofed email doesn't reach your customers or colleagues looking like it came from you.

Here's where a lot of people trip up. Starting with p=none is smart because it lets you monitor what's happening without affecting delivery. But p=none doesn't actually protect anyone. It's like installing a security camera with no alarm. You'll see the intruder after the fact, not stop them at the door.

The path forward is to move from p=none to p=quarantine, then to p=reject once you're confident all your legitimate sending sources are properly authenticated. Rushing to p=reject without that groundwork can block your own emails (of course, that's easier said than done when you're sending from a dozen different tools).

You can check your current DMARC record and see how it reads with our free DMARC Parser. If you're ready to generate your first record, the DMARC Generator walks you through it. Stuck on the policy rollout? Drop into our SOS hotline and we'll take a look with you.