§ VOL. 01 · N°042KILLBOUNCE · EMAIL VERIFIER
01. Cover

KillBounce.

§ The dekEvery bounce is the sound ofa burned lead.
§ Set in Big ShouldersPrinted in Cobalt
100 free creditsCredits never expireCredit-back guarantee
§ Try one, freeN° 042

§ What you can get back

Deliverable Risky Undeliverable? Unknown
Anonymous · No sign-up·5 checks / day / IP·Powered by KillBounce API
§ THE BOUNCE STOPS HERE◆ ◆ ◆
§ 01. Feature Set◆

3-Layer Verification

Syntax → DNS/MX → live SMTP probe. Each layer eliminates a class of bounce that the layer above misses.

Catch-All Detection

Accept-all servers get their own verdict. In-session probe distinguishes real mailboxes from anti-enumeration.

Bulk Verification

Drop a CSV, TXT or XLSX. Dedupe + status polling + segmented CSV download. Up to 5M addresses per job.

Privacy First

Your list is not our list. Encrypted transit + at rest. Results deleted on request. No resale, ever.

§ TRUSTED BY OPERATORS · N° 001◆
§ Featured lists
MailchimpHubSpotSalesforceBrevoSendGridKlaviyoActiveCampaignZapierMaken8nPostmarkAWS SESMailchimpHubSpotSalesforceBrevoSendGridKlaviyoActiveCampaignZapierMaken8nPostmarkAWS SES
§ 12 platforms · 1 clean list
§ 02. FeatureN° 042
§ Why this matters/ ISSUE ONE

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.

§ Without verification · after 1 sendCRITICAL

§ CRITICAL

35/100

Sender score

§ POOR

40%

Inbox placement

§ BLEEDING

$12,400

Wasted spend / month

§ With KillBounce · every sendHEALTHY

§ EXCELLENT

99/100

Sender score

§ HEALTHY

97%

Inbox placement

§ SAVED

$0

Wasted spend / month

§ Our fix

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

No subscription. Credits never expire. Credit-back guarantee if we say valid and it bounces.

§ Directional benchmarks — rounded from Litmus / HubSpot / Validity

22%

list decay per year

16.5%

avg. bounce rate without verification

30×

ROI on every clean email sent

§ 3 VITAL SIGNS◆ ◆ ◆
§ 03. FeatureN° 043
§ The 30-day spiral/ ISSUE TWO

One bad send.
30 days of fallout.

A worked example — sender score modeled from 92 to 8 across four weeks, benchmarked against the ESP throttling thresholds we see in practice.§ Illustrative model

§ Sender score · last 30 days
Without KillBounceWith KillBounce

§ Current reading

92/ 100Day 1
§ Fig. 01 — decay curve
0255075100DAY 1DAY 3DAY 7DAY 14DAY 30

§ Day 1 · Score 92

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.

§ SENDER SCORE◆ ◆ ◆
§ 03. The ProcessN° 043
§ How it actually works/ ISSUE THREE

From CSV
to clean list.
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.

01§ INTAKE

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
02§ GAUNTLET

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
03§ CLEAN

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

§ Batch size

5M

§ Formats

10+

§ Checks

03

§ Setup

00m

§ 3 STEPS · 0 SETUP◆ ◆ ◆
§ 03. DossierN° 073
§ The lab notebook · 2026/ VOL. IV

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 N° 01◆ ◆ ◆

§ Layer report · syntax → DNS → SMTP

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 N° 02◆ ◆ ◆
§ 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

§ Policy · zero-ticket refund

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 N° 03◆ ◆ ◆

§ Billing shape · pay-per-use

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 N° 04◆ ◆ ◆
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 · human replies

§ Support · a person, not a script

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

§ FOUR CLAIMS · FOUR ARTIFACTS◆ ◆ ◆ ◆
§ 03. FeatureN° 063
§ What you get/ CATALOG VI

Six things
you'll notice
in the first hour.

Each one survives a side-by-side with the household names. No fluff, no roadmap items dressed as features.

§ Catalog · six filesVI / VI
§ FILE · WARRANTYN° 01

Wrong-verdict refund

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

§ Proof

Credit

Refunded

←
§ FILE · PRICINGN° 02

$4 per 1,000 — no subscription

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

§ Proof

KillBounce
$4
Platform A
$7
Platform B
$8
Platform C
$9
§ FILE · WARRANTYN° 03

Catch-all flagging

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

§ Proof

valid@real.comok
foo@catchall.iorisky
anything@catchall.iorisky
random@catchall.iorisky
§ FILE · SECURITYN° 04

Encrypted, auto-deleted in 24h

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

§ Proof

24h
§ FILE · PLATFORMN° 05

REST API + 3 SDKs

Idempotent endpoints, OpenAPI 3.1 spec, official SDKs for Python, Node and PHP. Ruby + Go SDKs on the roadmap.

§ Proof

await client.verify('you@co.com')
§ FILE · PLATFORMN° 06

0–100 deliverability score

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

§ Proof

Valid

8.2K

Risky

412

Invalid

184

§ Colophon

Every file above ships on day one — not a roadmap. Priced at $4 per 1,000 verifications, credit-back guarantee if we say valid and it bounces.

§ 6 FILES · 1 PROMISE◆ ◆ ◆
§ 04. PersonasN° 048
§ For every team/ ISSUE FOUR

Different teams.
Same enemy:
bounces.

Marketing, engineering, agency ops, sales — each opens the same envelope. Pick your desk and read the brief.

A§ The brief · file A

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 expectLEDGER
01Bulk list cleaning
Up to 5M emails
02Verification layers
Syntax · DNS · SMTP
03Setup time
<5 min

§ On the manifest

  • Bulk list cleaning (up to 5M emails)
  • Catch-all & disposable detection
  • Spam-trap identification
  • CSV export for Mailchimp, HubSpot & any ESP
§ Use case · plate AMarketers

Pre-send list hygiene

Your campaigns, fewer bounces

§ At a glanceSPEC
Bulk list cleaningUp to 5M emails
Verification layersSyntax · DNS · SMTP
Setup time<5 min
§ CHOOSE YOUR CREW◆ ◆ ◆ ◆
§ 05. Developer KitN° 087
§ Developer experience/ VOL. 05

An API you'll
actually enjoy.

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

§ Ledger of guarantees03 / 03
  • N°01

    ~150ms median

    Single-call latency, 3-layer probe

  • N°02

    3 SDKs

    Python, Node, PHP (Ruby & Go coming)

  • N°03

    Async webhooks

    For batches over 10k emails

View full API docs

§ Live · versioned · idempotent

§ Live specimen · /v1/verifyPLATE 05·A
~/killbounce — python
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 }
§ Figure 05·A — single-call verifyMEDIAN 150ms · P99 380ms
§ REST · SDKs · WEBHOOKS◆ ◆ ◆
§ 100 FREE CREDITS ◆§ NO CREDIT CARD ◆§ CREDITS NEVER EXPIRE ◆§ CREDIT-BACK GUARANTEE ◆§ $4 PER 1,000 VERIFIES ◆§ 100 FREE CREDITS ◆§ NO CREDIT CARD ◆§ CREDITS NEVER EXPIRE ◆§ CREDIT-BACK GUARANTEE ◆§ $4 PER 1,000 VERIFIES ◆§ 100 FREE CREDITS ◆§ NO CREDIT CARD ◆§ CREDITS NEVER EXPIRE ◆§ CREDIT-BACK GUARANTEE ◆§ $4 PER 1,000 VERIFIES ◆

§ Start smart. Stay clean.

Verify your first 100 emails free.

Get 100 credits
§ 05. PricingN° 120
§ Pay per email/ ISSUE ONE

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, no seat fees.

§ Live estimate · Premium packREF-06 / 9

§ You pay

$120

One-time · credits never expire

§ Per email

$0.0012

Cheaper the more you buy

§ Credits

100,000

Emails you can verify

Drag to size
1K10K50K200K1M

§ Redeem

100,000 credits
for $120.

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

§ Or pick a popular sizeCLICK TO JUMP THE SLIDER
§ 9 PACKS · 0 SUBSCRIPTIONS◆ ◆ ◆
§ 09. Reader Q&AN° 099
§ Anything else on your mind?/ ISSUE NINE

The questions
buyers actually
ask us.

Four chapters, real answers, no marketing rinse. Jump to the column that matters — the rest keeps for later.

§ Select a chapter4 SECTIONS · 4 ENTRIES
§ CHAPTER I · Billing & creditsPAGE 01 / 04
No. Buy 10,000 today, use them next year — the bill is the same.

§ Errata & correspondence

Still have a question?
Real engineers reply.

First response within one business day. No support-ticket maze, no chatbot triage — just a human at the other end.

Talk to us
§ Chapters I—IV◆ ◆ ◆
§ 09. EnlistN° 100
§ Ready when you are

Stop sending
into the void.

One hundred verifications on the house. No card. No subscription. First bounce-proof send in under two minutes.

§ What you get on sign-up03 · GUARANTEES
§ 01

No credit card

Card asked only at top-up

§ 02

Credits never expire

Buy once, use forever

§ 03

2-min setup

Paste list → verify → send

§ CREDIT-BACK GUARANTEE◆ ◆ ◆