Letterhead

Free tool · SPF checker

Free SPF checker

Type your sending domain to see its SPF record and whether receivers will trust it. We flag a missing record, two records at once and settings that vouch for anyone, and check DKIM and DMARC while we’re there. 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 SPF

What an SPF record does

SPF (Sender Policy Framework) is a TXT record on your domain that lists the servers allowed to send mail as you. When Gmail or Outlook receives a message from your domain, it checks the server that sent it against that list.

A typical record looks like v=spf1 include:_spf.google.com include:mail.example-esp.com ~all. Each include: adds a service that sends for you, and the ending says what to do with everyone else.

The three mistakes the checker flags

  • No record. Gmail and Yahoo expect SPF from anyone sending in bulk.
  • Two records. A domain can publish only one SPF record. With two, receivers ignore both, so merge them into one.
  • An ending that vouches for anyone. +all, ?all or no all means any server passes. End with ~all or -all.

Every sender goes in the one record

Your newsletter platform, Google Workspace or Microsoft 365, your CRM and any other tool that sends as your domain all belong in the same record. SPF also allows at most 10 DNS lookups per check, and every include: counts toward it. The checker doesn’t count lookups yet, so if your record has many includes, check that number too.

SPF checks the server, not the message, and it often breaks when mail is forwarded. That’s why receivers want DKIM and DMARC alongside it.

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.
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FAQ

Questions about SPF

What is an SPF record?

A TXT record on your domain, starting v=spf1, that lists the servers and services allowed to send mail as you.

Can a domain have two SPF records?

No. If a domain publishes two, receivers treat SPF as broken and ignore both. Combine every include: into one record.

Should my SPF record end in ~all or -all?

Either works for a newsletter. ~all (soft fail) asks receivers to accept but mark mail from unlisted servers; -all (fail) asks them to reject it. ~all is the safer choice while you’re still finding every service that sends for you. Never use +all.

Is SPF enough on its own?

No. Gmail and Yahoo expect SPF, DKIM and DMARC from bulk senders, and DKIM still works when mail is forwarded, where SPF often fails.

Do you keep the domain or email I check?

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

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