Bounce prevention, before you press send

Verify 1,000 emails in 60 seconds for $4.

Syntax, DNS, and a live mailbox probe — every address scored 0–100 before it ever reaches your sending tool. $4 per 1,000. Credits never expire.

Try it now

100 free credits to start
No credit card
Results in seconds

$4 per 1,000
Credits never expire
Refund if it bounces

Export clean lists into your current tools

Native integrations are on the roadmap; today we hand off via CSV / API. The list works with all of these.

MailchimpHubSpotSalesforceBrevoSendGridKlaviyoActiveCampaignZapierMaken8nPostmarkAWS SESMailchimpHubSpotSalesforceBrevoSendGridKlaviyoActiveCampaignZapierMaken8nPostmarkAWS SES

Why this matters

One bad list. Years of trust. Burned in a week.

Three vital signs on a 50K list at a 12% bounce rate — before and after a single verified send.

your-domain.com / health3 alerts

Without verification — after 1 send

CRITICAL

0/100

Sender score

POOR

Inbox placement

BLEEDING

Wasted spend / month

same domain · with KillBounce

With verification — every send

EXCELLENT

0/100

Sender score

HEALTHY

Inbox placement

SAVED

Wasted spend / month

Our fix

$4 per 1,000 verifications flips these red bars to green.

No subscription. Credits never expire. Refund if we say valid and it bounces.

list decay per year

Source · Industry CRM benchmark

avg. bounce rate without verification

Source · Email infra report

0×

ROI on every clean email sent

Source · Marketing assoc. study

The 30-day spiral

One bad send. 30 days of fallout.

Sender score from 92 to 8 in four weeks. Every point on this curve maps to real ESP throttling thresholds — not theory.

Sender score · last 30 days

92/ 100Day 1

Without KillBounceWith KillBounce

Day 1

You hit send

12% of addresses bounce. The ESP starts taking notes. You don't feel it yet.

Our fix

Skip the timeline. Verify first.

3-layer probe catches the dead, the risky, and the traps in one pass. $4 per 1,000 — no subscription, credits never expire.

How it actually works

From CSV to clean list. Usually under a minute.

Three steps. No setup, no SQL, no CSV gymnastics. Drop in a list, get a verified one back — $4 per 1,000.

Drop in your list

CSV, TXT, XLS, or paste. Up to 5M addresses per job. We dedupe before you even hit verify.

Drag & drop or paste
Auto-deduplicate
10+ formats

We run the gauntlet

Each address passes three checks: syntax, DNS/MX, live mailbox probe. We catch what regex never could.

Syntax + format
MX & catch-all
Live mailbox probe

Take the clean list

Categorized results with a reason code per address. Export CSV, ping a webhook, or pipe straight to your ESP.

CSV in one click
Reason codes
API + webhooks

The lab notebook · 2026

Four claims. Four artifacts.

Four guarantees in the product, each shown with the actual mechanic that backs it — the probe, the refund format, the payment shape, the support model.

Exhibit · probe trace

Three layers. Not one.

The actual probe we run on every address — syntax, DNS/MX, then a real in-session SMTP conversation with the recipient mail server. We hang up before DATA, so no message is sent.

→ Verifiable in /api-docs

kb · probe · nikhil@getkillbounce.com (illustrative)

$ kb probe nikhil@getkillbounce.com    # illustrative trace

[layer 1: syntax]   ✓ ok — RFC 5322 compliant
[layer 2: dns]      ✓ ok — 1 MX: aspmx.l.google.com

[layer 3: smtp]     220 mx.google.com ESMTP
                    > EHLO killbounce.com
                    250-mx.google.com at your service
                    > MAIL FROM:<probe@killbounce.com>
                    250 OK
                    > RCPT TO:<nikhil@getkillbounce.com>
                    250 2.1.5 OK
                    > RSET                  ← we hang up here
                    250 OK (no mail sent)
                    > QUIT
                    221 closing connection

✓ verdict: VALID · score 96 · 412ms

Exhibit · the credit-back guarantee

Refund event · templateformat

When: You forward the bounce notification to support@
What triggers: A 5.x.x SMTP rejection on an address we returned Valid
How long: Within five business days of receipt
What returns: +1 credit per refunded verification, back to your balance
What you pay: Nothing extra — no service fee, no review charge
What does not refund: Soft bounces, complaints, list-decay outside the window

Mechanic · written into the policy/refund-policy

Backed by a credit-back guarantee.

Every verification we mark Valid is backed by the format on the left. If the actual send hard-bounces, the credit returns to your balance automatically — no support ticket, no debate.

→ /refund-policy

Exhibit · 12-month ledger

No subscriptions. Ever.

The standard model in this category is a monthly bill that charges you whether you sent anything or not. KillBounce is one-time packs — pay when you buy, then keep using until the credits run out.

→ /pricing

10,000 addressesJFMAMJJASONDYear

A monthly verifier

paid every month

12 × monthly fee

KillBounce

one-time pack

just the pack

Same workload · 12 monthsYou owe us for one

Exhibit · what a reply looks like

Fromsupport@getkillbounce.comToyouSubjectRe: [your question]

Hi —

Short answer: [the actual fix for your situation].

Longer version: one to three paragraphs that explain the technical reason, cite the relevant RCPT TO /250 OKbehavior or refund-policy clause, and tell you what we'd change on your account if it helps.

If we got it wrong on your list, send the bounce notification and the credit comes back. Reply to this email — same thread.

— The KillBounce team

support@getkillbounce.com · Bengaluru

Replies come from someone who built it.

The format on the left is what every support reply takes — a specific answer to your specific question, with the policy or protocol reference, plus what we'd change on your account if relevant. No tier system, no canned templates.

How support is shaped

First reply within one business day, on the working week.
Reply comes from a person who can read the code, not a script.
Edge cases & account flags handled in the same thread, no escalation tier.

→ support@getkillbounce.com

What you get

Six things you'll notice in the first hour.

Each one survives a side-by-side with the household names. No fluff.

Wrong-verdict refund

If we mark an address valid and it bounces, the credit is auto-refunded. No ticket, no review.

Credit

Refunded

←

$4 per 1,000 — no subscription

Same 3-layer probe as the household names (syntax, DNS, SMTP). Credits never expire.

KillBounce

Platform A

Platform B

Platform C

Catch-all flagging

Domains that accept anything and silently drop mail are tagged risky — never falsely passed as valid.

valid@real.comok

foo@catchall.iorisky

anything@catchall.iorisky

random@catchall.iorisky

Encrypted, auto-deleted in 24h

AES-256 at rest, TLS 1.3 in flight. Lists purge after 24 hours. Zero-retention mode on request.

24h

REST API + 5 SDKs

Idempotent endpoints, OpenAPI 3.1 spec, official SDKs for Python, Node, PHP, Ruby, Go.

await client.verify('you@co.com')

0–100 deliverability score

Drill into any address, see which of the 3 layers failed, and export the slice to CSV.

Valid

8.2K

Risky

412

Invalid

184

For every team

Different teams. Same enemy: bounces.

Stop training Gmail to filter you

Every bounce nudges your sender score down. Clean the list before the campaign — keep the inbox door open.

What to expect

Bulk list cleaning

Up to 5M emails

Verification layers

Syntax · DNS · SMTP

Setup time

<5 min

Bulk list cleaning (up to 5M emails)
Catch-all & disposable detection
Spam-trap identification
Native Mailchimp & HubSpot flows

Use case

Pre-send list hygiene

Your campaigns, fewer bounces

Bulk list cleaningUp to 5M emails

Verification layersSyntax · DNS · SMTP

Setup time<5 min

Developer experience

An API you'll actually enjoy.

REST endpoints, typed SDKs, idempotent calls, async webhooks. Every response includes a 0–100 deliverability score. $4 per 1,000 verifications — no subscription.

~150ms median
Single-call latency, 3-layer probe
5 SDKs
Python, Node, PHP, Ruby, Go
Async webhooks
For batches over 10k emails

View full API docs

12345678910

import killbounce

client = killbounce.Client(api_key="...")

result = client.verify("test@example.com")

if result.status == "valid":
    print(f"✓ Deliverable — score {result.score}")
else:
    print(f"✗ {result.reason}")

Response200 · 142ms · { status: "valid", score: 97 }

Pricing

Pay for what you check. Nothing else.

Slide to your list size. Every price is a real pack you can buy — no subscriptions, no minimums.

Premium pack — you pay

$120

one-time payment · credits never expire

Per email

$0.0012

cheaper the more you buy

How many emails?100,000

1K10K50K200K1M

No card to start · 100 free credits · cancel by closing the tab

Or pick a popular size

click a tier to jump the slider

Last-mile questions

Anything else on your mind?

The questions buyers actually ask, grouped so you can jump to what matters.

No. Buy 10,000 today, use them next year — the bill is the same.

Still have a question?

Real engineers reply, usually under 10 minutes during business hours.

Talk to us

Free100Credits

Ready when you are

Stop sending into the void.

Get 100 free credits. No credit card. Set up in under 2 minutes.

No credit card

Cancel anytime

2-min setup