Letterhead

Free tool · DMARC checker

Free DMARC checker

Run a DMARC lookup on your sending domain to see whether it publishes a policy that Gmail, Yahoo and Outlook will find. We check SPF and DKIM at the same time, since DMARC depends on both. Free, no signup.

We check the DKIM selectors Google Workspace, Microsoft 365 and the big email platforms use. If yours isn’t one of them, paste the full source of an email you sent, as it arrived (in Gmail: “Show original”), into “Check an email” and we’ll read it from there.

Know your DKIM selector?

It’s the s= value in an email’s DKIM-Signature header.

About DMARC

What DMARC does

DMARC is a TXT record at _dmarc.yourdomain.com. It tells receivers what to do when a message claiming to be from you fails the SPF and DKIM checks for your domain, and where to send reports about it.

The minimum record is v=DMARC1; p=none;. Most senders add rua=mailto: and an address, so receivers send them aggregate reports.

p=none, quarantine and reject

  • p=none asks receivers to take no action and just report. It meets the Gmail and Yahoo requirement, and it’s where everyone starts.
  • p=quarantine asks them to treat failing mail as suspicious, usually by sending it to spam.
  • p=reject asks them to refuse it. Move here once your reports show all your real mail passing.

Who requires it

Gmail and Yahoo have required SPF, DKIM and a DMARC policy from anyone sending more than 5,000 messages a day to their users since February 2024. Outlook.com has rejected bulk mail that fails them since May 5, 2025.

Subdomains

If you send from news.example.com and only example.com publishes DMARC, the parent’s policy covers you. The checker shows that as Covered, and warns you when the main domain doesn’t publish exactly one DMARC record.

In Letterhead, these checks run while you write.

Every issue gets a content check before it goes out: bounce risk, links that won’t work, what an AI inbox will read, readability, and email weight with what’s making it heavy. Letterhead also strips redundant styling from what it sends, so your newsletter goes out lighter than you wrote it.

The old wayIn Letterhead
Find out Gmail clipped you when a reader asks where the unsubscribe link went.Email Weight shows how heavy every issue is, and what’s making it heavy, before you send.
Click every link by hand the morning of the send.Links with no working destination are flagged in the editor before you send.
Paste the HTML into another tool to slim it down.Letterhead strips redundant styling from what it sends, so it goes out lighter than you wrote it.
Book a test drive

FAQ

Questions about DMARC

Do I need DMARC to send a newsletter?

If you send more than 5,000 messages a day to Gmail or Yahoo addresses, yes. Both have required SPF, DKIM and a DMARC policy from bulk senders since February 2024, and Outlook.com has rejected bulk mail that fails them since May 2025. v=DMARC1; p=none; is the minimum.

What’s the minimum DMARC record?

v=DMARC1; p=none; published as a TXT record at _dmarc.yourdomain.com. Add rua=mailto:you@yourdomain.com if you want reports.

Should I use p=none, quarantine or reject?

Start with p=none and read your reports. When they show every service that sends as you passing SPF or DKIM, move to quarantine, then reject.

Why am I getting DMARC reports?

Your record has a rua= address, so receivers send it summaries of mail claiming to be from your domain. They’re how you spot services sending as you that SPF or DKIM don’t cover yet.

My domain has two DMARC records. Is that a problem?

Yes. Receivers ignore both, so it’s as if you had none. Keep one.

Do you keep the domain or email I check?

No. We don’t store what you paste or the domain you look up.

More free checks

Check the rest before you send.

All free tools