Every check that
actually protects
your sender reputation.
KillBounce isn't a regex pretending to be a verifier. We open real SMTP conversations, spot catch-alls and spam traps, and tell you exactly why each address passed or failed.
Three layers.
Every address.
Every time.
Each layer catches what the previous one couldn't. Anything we can't confirm comes back as "unknown" — no fake confidence.
Syntax & format
RFC 5321 + 5322 compliant. Catches typos (gnail.com), invalid characters, length violations, and the dozen other ways email addresses go wrong before they leave the keyboard.
DNS & MX records
We resolve the domain, look up MX records, and check whether mail can even be routed there. Domains that point nowhere don't cost you a credit.
Live SMTP mailbox probe
We open an SMTP conversation with the receiving server and ask whether the mailbox accepts mail. No mail is sent — we hang up before DATA. This is the check that catches everything else.
What gets
flagged.
Beyond "valid / invalid." We tag every risk so you can decide.
Catch-all domains
Domains that accept any address and silently delete what they don't want. Flagged as risky.
Spam traps
Recycled and pristine traps. One hit = blacklist. We flag known traps before you send.
Disposable / temp
10,000+ disposable domains tracked. Mailinator, TempMail, Guerrilla — all flagged.
Role accounts
info@, admin@, sales@. Often filtered, often shared. Flagged so you can decide.
Fast where
it counts.
§ Verification layers
3
Syntax + DNS + live SMTP
§ Bulk processing
Async
Parallel, rate-limited per domain
§ API response time
~150ms
Single verifications
§ Guarantee
Credit-back
Verifiably wrong = credit back
Drop into
your stack.
API-first, but UI-complete. Pick the integration that matches your workflow.
REST API
OpenAPI spec, idempotent calls, bearer auth. SDKs in progress for Python and Node.
Webhooks
Async batch jobs ping your endpoint when complete. Retried with backoff on failure.
CSV / Excel
Drag and drop. We auto-detect columns, dedupe, and normalize before verifying.
No-code glue
Anything that speaks HTTP can call the API — Zapier, Make, n8n, or a 10-line script. No prebuilt ESP connector yet.