Free email security check

Somebody may be sending email as you.

See in ten seconds whether your domain is protected against spoofing. DMARC, SPF and DKIM, graded A to F.

Free · no account needed Add the ending too, like yourdomain.com

Chapter one

Your domain is a return address anyone can write on an envelope.

Email was designed in 1982 with no way to prove who sent a message. Forty years later the fix exists — three DNS records — but most domains still have the door open.

SPF lists the servers allowed to send for you. DKIM signs each message so it cannot be altered. DMARC ties them together and tells receiving servers what to do when a message fails: nothing, quarantine it, or reject it.

Only the last one stops spoofing. Getting there without blocking your own mail is what this product is for.

Chapter two

One line of text, read by every mail server on earth.

This is a DMARC record. Select a tag to see what it does — the red one is the tag that actually stops spoofing.

Enforcement Reporting to argus0
Chapter three

The reports you were never going to read.

Every receiving provider sends a compressed XML file, daily, per domain. We collect them, parse them and show what matters: who sent, how much, and whether it passed.

google.com · aggregate report example of a parsed report
209.85.220.41
Google Workspace
DMARC pass
4,120
198.2.128.9
Mailchimp
DMARC pass
1,004
185.220.101.4
Unknown · Netherlands
DMARC fail
2,918
51.15.22.7
crm.example.net
DKIM misaligned
61
Chapter four

From “none” to “reject”, without breaking your own mail.

Tightening the policy too early blocks your newsletter, your CRM, your invoices. We show you every sender, whether it aligns, and for how long — so you can see the moment nothing legitimate is still failing. The decision is yours, and so is the record: your zone stays yours, and we hold no key to it.

p=none

Observe. Reports arrive, nothing is blocked. Most domains stop here forever.

p=quarantine

Failures go to spam. Safe once your senders pass at 98%+ for a few weeks.

p=reject

Spoofed mail is refused before it lands. Move here once your own senders have been passing for weeks — the reports show you when.

argus0 is also an MCP server — ask your AI assistant “any spoofing overnight?” and the answer comes from your own reports. How that works →

Find out who is writing your name today.

Free for 3 domains and 7 days of reports. Starter, Pro and Enterprise from there.