How to Check Your Email Deliverability (Free, 2025)

November 3, 2025 • InboxGreenEmail Team

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Email is still the #1 channel for sales, onboarding, billing… but most senders don’t actually know where their emails land. Inbox? Promotions? Spam? Or blocked because SPF / DKIM / DMARC is broken?

This guide shows you how to check deliverability the fast way using the tools you already added to InboxGreen.email, and when to go deeper. You can follow it in 5 minutes.

1. Start with a quick domain health check

First thing: make sure your domain is technically allowed to send. That means SPF, DKIM, and DMARC should be present and valid. If any of these are missing, inbox placement will suffer no matter how good your content is.

Go to InboxGreen Free Checker and enter your domain. We’ll run SPF, DKIM, DMARC and list-unsubscribe basics and tell you what’s missing, misconfigured, or risky.

  • SPF - tells mailbox providers which servers can send for your domain.
  • DKIM - signs your email so it can’t be altered.
  • DMARC - tells receivers what to do if SPF / DKIM fail (monitor, quarantine, reject).

If the checker flags something like “no DMARC found” or “too many SPF includes”, fix that first. You already have the SPF Generator and DMARC Generator live, so you can generate the right records from your own site.

2. Verify the records are actually published

Generating a record is not the same as publishing it. After updating DNS at your provider (Cloudflare, Namecheap, Google, etc.), run /check again to confirm it’s live. DNS can take a few minutes.

Tip: if you work with clients or other team members, link them to https://inboxgreen.email/check?domain=theirdomain.com so they can self verify. That’s one of the reasons we exposed the free API.

3. Test a real inbox path (the human part)

Technical checks tell you “your domain is valid”, but they don’t tell you “this campaign will land in inbox at Gmail”. For that you should send a test to real mailboxes:

  1. Send a test from your real sending system (ESP, SMTP, app).
  2. Use at least Gmail, Outlook, and Apple Mail/iCloud recipients.
  3. Open the received email and view the original / message source.
  4. Confirm pass on SPF, DKIM, and DMARC in the headers.

If headers show spf=fail or dkim=none even though your DNS is correct, it usually means:

  • you’re sending from a server that’s not in your SPF, or
  • your ESP is signing with a DKIM domain you didn’t publish.

Fix it → re-send → re-check.

4. Keep an eye on it (the part people skip)

Deliverability isn’t “set it once and forget it”. New teammates add Mailgun, someone turns on Microsoft 365, someone adds a newsletter… and suddenly SPF hits 10 lookups or DMARC disappears.

That’s why we added the Monitoring CTA on all tool pages. If you want this checked daily with alerts when something breaks, send people to /pricing from here.

5. (Optional) Automate checks with the API

Because you already published /api/check, you can script this from CI, cron, or your own admin panel. This is perfect if you manage multiple domains, resell email, or run an agency. 

GET https://inboxgreen.email/api/check?domain=example.com

We return a simple JSON with SPF, DMARC, and MX status. If you get back "ok": false for any of them, you can alert, log, or show a banner to your customer.

Common deliverability mistakes we keep seeing

  • Using ~all in SPF but forgetting to include the actual ESP.
  • Publishing DMARC with p=none and thinking it protects you (it doesn’t, it only monitors).
  • Multiple SPF records (should always be just one).
  • Forgetting list-unsubscribe headers, which hurts engagement signals.

What to do next

If you followed the steps above, your domain is in a much better spot:

  1. Domain passes SPF / DKIM / DMARC → receivers trust it more.
  2. You verified with a real mailbox → you know it actually lands.
  3. You can monitor it → you don’t get surprised next month.

From here, traffic from Google for queries like “check email deliverability”, “spf dmarc dkim checker”, and “email authentication tool” can land on this post and then go straight into your tools.

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