See a real verdict in under a second.
Paste any email. We'll run the same regex, MX, disposable, and SMTP probe we run for our paid API — and tell you whether you should send to it. No signup, no API key. Three free checks per visitor.
Continue past three? Sign up free and we lift the cap with your tier.
Three free checks per visitor. After that, sign up to keep going.
What makes Sigilpost different.
Most email checkers only look at two things: did it bounce, and how much did it cost. Sigilpost tells you the truth about hard-to-verify addresses — and earns a clear yes or no.
We catch email addresses that are hard to verify
Some addresses look fine on the surface but accept anything. Other tools guess and call it good. We test those hard cases against a 14-step checklist — and we publish the results so you can compare us to the rest.
We check emails the gentle way
We open one connection at a time, say hello, and walk away. We never retry, never queue mail, and never push the same server too hard. Your sender reputation stays clean — and so does the receiver's patience.
Your data stays private
We don't keep emails longer than you want. We don't enrich them with extra data. And if you're in Europe, you can pick EU-based servers on bigger plans. A signed data agreement comes with every paid plan.
Send an email, get a yes or no.
Try three free checks on the homepage — no signup. The JSON below is what you get back, shortened for display.
curl https://api.sigilpost.dev/v1/verify \
-H "Authorization: Bearer $SIGILPOST_KEY" \
-d '{"email":"jordan@stripe.com","checks":["mx","disposable","smtp"]}'{
"email": "jordan@stripe.com",
"verdict": "valid",
"score": 94,
"mx": "google.com",
"disposable": false,
"role": false,
"free": false,
"catch_all": false,
"smtp_state": "ok",
"latency_ms": 387,
"request_id": "sgl_8a13…f0c2"
}How we compare to other tools.
We ran the same 50,000-address test set through each provider's public API last quarter. See the full matrix, per-competitor summaries, and the test harness.
| Provider | Accuracy | Speed | Price per 1,000 | Public audit |
|---|---|---|---|---|
| Sigilpost· us | 99.4% | 387 ms | $5.80 | Yes |
| ZeroBounce | 97.1% | 612 ms | $8.00 | Partial |
| NeverBounce | 96.8% | 701 ms | $8.00 | Partial |
| Hunter | 94.2% | 488 ms | $9.00 | No |
| Clearout | 95.6% | 954 ms | $7.00 | No |
| Listmint | 92.7% | 1.12 s | $6.50 | No |
Pay only for what you check.
One credit covers one check. Larger plans raise the cap, and downgrading is instant — you only pay for what you've used.
5,000 checks / mo
- One API key
- Up to 256 checks per second
- US-based servers
- Email support
25,000 checks / mo
- Up to 5 API keys
- Up to 512 checks per second
- Webhook callbacks
- Bulk check endpoints
- Audit-ready request logs
- EU servers available
100,000 checks / mo
- Unlimited keys
- Up to 1,024 checks per second
- Custom probe timing
- Dedicated success manager
- SAML SSO
- 99.95% uptime SLA
- Onboarding engineering hours
Common questions.
Does a check cost a credit even if we already verified it today?
No. The same email checked again within 24 hours reuses the prior result for free. The cache key is the email plus your chosen checks — never your API key.
What if the mail server is behind a firewall?
We mark the result as 'risky' and lower the confidence score by 25 points. We never silently fold a blocked server into 'valid' the way some competitors do.
Can I bring my own check?
Yes, on the Scale plan. You send us a signed probe manifest; we orchestrate the callout and report the verdict band you define. Useful for some regulated workflows.
How long do you keep my data?
Default is 7 days on Starter, 30 days on Growth, and up to 90 days on Scale. We delete payload bytes on a schedule and keep only a one-line audit row with no personal info.
Do you enrich the email?
No. We never resolve names, employers, or social-graph data. Enrichment is the privacy anti-pattern other tools ignore, and we skip it on purpose.
Try three free checks. No signup.
No signup wall. Try the endpoint as a guest, then email us to unlock keys, bulk endpoints, and the audit log.