Best Free SPF, DKIM & DMARC Checker Tools (2026)

If your emails sometimes vanish into spam folders — or never get answered even though you know the recipient exists — the problem is rarely the words in the email. It's almost always three DNS records with intimidating names: SPF, DKIM and DMARC. They exist so that Gmail, Outlook and every other mail provider can verify that an email claiming to be from your domain actually came from you, and not from a spammer pretending to be you. Get them wrong (or leave them missing) and your legitimate emails get treated like spam. The good news: checking them takes about 10 seconds with the right tool, and several of the best ones are completely free.

The short version: for a quick free check, mailX and IntoDNS.ai give the clearest plain-language explanations of what's wrong. If you want a single score to track over time, EmailQo's grader is the simplest. Developers who prefer raw DNS lookups over hand-holding will like SPF Toolbox. To test an actual sent email (not just the domain config), dkimvalidator.com and mail-tester.com are the standard. And if you're building or sending product emails and need ongoing deliverability protection built into the sending pipeline itself, MailerLogic is worth a look instead of a one-off checker.

1. mailX — best plain-language explanations

mailX is a free DNS lookup and email deliverability toolkit that checks your domain's authentication records (SPF, DKIM, DMARC, BIMI), scans blacklists, and — unlike most checkers — explains the results in plain English instead of dumping raw DNS output on you. It also ships a JSON API and an MCP server, so an AI coding agent can run the check for you and fix the records directly.

Pricing: 100% free, no signup.

Verdict: the best starting point if you don't already know what SPF/DKIM/DMARC mean — it teaches you while it checks. The tradeoff is that it's a small team's free tool with no continuous monitoring, so re-run it after any DNS change rather than expecting alerts.

2. IntoDNS.ai — best for AI-generated fix suggestions

IntoDNS.ai checks SPF, DKIM, DMARC, DNSSEC, BIMI, MTA-STS and 40+ blacklists in one pass, then uses AI to explain what's wrong and suggest the exact record to add. Free, no signup required.

Pricing: 100% free.

Verdict: good second opinion alongside mailX — it checks a wider net of standards (DNSSEC, MTA-STS included), but the feature set is thinner for advanced users who already know what they're looking for.

3. EmailQo Email Infrastructure Grader — best for a single trackable score

EmailQo's grader checks SPF, DKIM, DMARC and mail server configuration, then scores any domain out of 100. No signup required for the free check; advanced options are available on quote.

Pricing: free grade; advanced features on request.

Verdict: the 0-100 score is the easiest way to explain deliverability health to a non-technical teammate or track improvement over weeks, but it's a less-known tool with limited support if you get stuck interpreting a low score.

4. SPF Toolbox — best for raw DNS lookups (open source)

SPF Toolbox is a simple, open-source (MIT license) app for looking up SPF, MX, Whois and other DNS records directly, without extra commentary.

Pricing: free.

Verdict: best for developers who want the raw record and nothing else — no AI explanations, no scoring, just the DNS data. Being open source (PHP, MIT), you can also self-host it. Feature set is intentionally minimal.

5. dkimvalidator.com — best for testing an actual sent email

dkimvalidator.com, a free service by roundsphere.com, works differently from the tools above: instead of checking your domain's DNS in isolation, you send a real test email to an address it gives you, and it reports back whether that specific email's SPF/DKIM/DMARC passed — which is a closer simulation of what Gmail actually sees.

Pricing: free.

Verdict: the right complement to a DNS-only checker, because it tests your actual sending setup (mail server, headers included) rather than just the DNS records. Feature set is narrow and the tool is not widely known, but it does the one job well.

6. mail-tester.com — best overall deliverability score for a test send

mail-tester.com is the most widely used tool in this category: send a test email to the address it provides and it grades SPF, DKIM, DMARC, content, and spam-trigger factors, with 20 free tests per month.

Pricing: free, 20 tests/month.

Verdict: the closest thing to an industry standard for "will this specific email land in spam" — clear results, widely trusted. The monthly cap of 20 tests is the only real limit, and advanced/ongoing monitoring isn't included.

7. MailerLogic — best if you need deliverability built into sending, not just a checker

MailerLogic is a different kind of tool: a full email delivery platform (transactional API, SMTP relay, CRM) with deliverability intelligence built in — it checks SPF/DKIM/DMARC and flags risky content before you send, and separates transactional traffic from marketing traffic by default to protect your sender reputation.

Pricing: Freemium — free for 200 emails/month, Starter $9/month (10,000 emails), Professional $12/month, Enterprise on quote.

Verdict: worth it once you're past the "check once" stage and are actually sending product emails at volume — the built-in reputation protection and low entry price ($9-12/month) are strong for a SaaS on a budget. It has less of a track record than established players like SendGrid, Postmark or Mailgun, so weigh that if reliability at scale is critical.

None of this requires a budget. The realistic workflow is: run your domain through mailX or IntoDNS.ai to catch missing or broken SPF/DKIM/DMARC records, fix what they flag, then confirm with a real send test on mail-tester.com or dkimvalidator.com before you trust the setup. Only reach for a platform like MailerLogic once checking manually stops being enough — for example, once you're sending transactional email at real volume and a single misconfigured campaign could tank your whole domain's reputation.