Enterprise-Grade
Online Email Verifier
Stop hard bounces and protect your sender score. Clean bulk CSV & Multi-Sheet Excel (.XLSX) workbooks or test single emails via real-time 7-Layer Smart SMTP.
Auto-detects your email column · Supports .CSV, .XLS & Multi-Sheet .XLSX
- > Engine Ready · 7-Layer Live SMTP & Disposable Check Active
- > Upload a CSV/Excel file or click a Sample button above to watch live verification...
High-Speed Email Verification
7-Layer Live Verification
Stop guessing. Our multi-stage verification engine checks syntax, DNS/MX records, disposable databases, and live SMTP handshakes to protect your sender reputation.
Zero Data Retention
Your privacy is built into our architecture. Files are processed strictly in volatile RAM and purged immediately after verification. We never store or resell your lists.
Stop Paying for Dead Leads
CRMs and ESPs charge by subscriber count. Remove invalid, disposable, and role-based addresses before importing so you only pay for real, reachable contacts.
Explore our verification tools & guides
How KaijuVerifier Works
Clean any CSV or Multi-Sheet Excel workbook in under 60 seconds with zero setup.
1. Upload CSV or .XLSX
Drag and drop your `.csv`, `.xls`, or multi-sheet `.xlsx` file. Our engine automatically finds the email column across your sheets.
2. 7-Layer SMTP Scrubbing
We validate syntax, DNS/MX records, 1M+ disposable domains, role accounts, catch-all servers, and live SMTP mailbox responses in parallel.
3. Download Clean Workbook
Export your deliverable leads, invalid report, or your original multi-sheet Excel workbook with only bad emails removed.
Clean Your Email List — The Complete Solution
Our multi-layer verification engine goes far beyond basic syntax checks with real-time SMTP handshakes and intelligent domain filtering.
4-Stage Core Verification Pipeline
Syntax & RFC 5322 Validation
First line of defense. We verify email format follows strict RFC 5322 standards, checking structure, invalid characters, and domain typos.
DNS & MX Record Inspection
We query live DNS records to confirm the domain exists and has active Mail Exchange (MX) servers configured to receive messages.
Live SMTP Handshake
Real-time SMTP protocol verification (`EHLO` / `RCPT TO`) connects directly to the mail server without sending an actual email.
Mailbox Activity & Quota Check
Verifies that the specific recipient mailbox is active and able to receive mail, flagging disabled accounts and full inboxes.
Advanced Threat & Risk Filtering
Disposable Email Detection
Continuously updated database of 1M+ disposable & burner domains (Temp-Mail, Guerrilla Mail, 10MinuteMail, Mailinator).
Toxic & Spam-Trap Blocking
Curated blocklist of toxic and abusive domains known for spam complaints, honeytraps, and bot activity.
Spam Pattern Filtering
Detects 110+ high-risk patterns including spam keywords, keyboard-mash strings, and automated bot signups.
Role-Based Account Flagging
Flags shared group inboxes (`info@`, `support@`, `sales@`, `admin@`) that lower cold-outreach engagement and GDPR compliance.
Built for Real Spreadsheet Workflows
Deliverability & Sender Reputation Protection
Hard Bounce Removal
Eliminate permanent delivery failures caused by non-existent mailboxes, dead domains, and deactivated employee accounts.
Soft Bounce Diagnosis
Detect temporary issues like full mailboxes, rate-limited servers, or transient MX errors before launching your campaign.
Catch-All Domain Detection
Identify corporate mail servers configured as `accept-all` so you can segment high-confidence leads from catch-all domains.
Greylisting-Aware Retries
Smart detection of mail servers using greylisting anti-spam defenses, preventing false negatives on valid corporate emails.
Built for Precision, Privacy & Real Workflows
Everything enterprise senders expect from ZeroBounce or NeverBounce — at up to 80% lower cost and with native multi-sheet Excel support.
Multi-Sheet Excel (.XLSX) Preservation
Other verifiers force you to flatten workbooks into single-sheet CSVs. Upload a multi-tab .xlsx workbook and download it back with every sheet, column, and tab name intact.
Zero-Retention In-Memory Scrubbing
Your customer lists are processed strictly in volatile RAM and purged immediately upon completion. We never store, resell, or log your raw email contacts on disk.
MX Fingerprinting & Deep SMTP
Beyond static blacklists, our engine fingerprints MX server clusters in real time to catch brand-new burner domains, catch-all servers, greylisting, and role accounts.
Frequently Asked Questions
Is it really free?
Yes — the free plan includes 100 verifications per month with no credit card required. One-time credit packs start at $19 for 5,000 credits (never expire), and monthly plans start at $19/mo for 10,000 verifications.
How accurate is the verification?
We use a comprehensive 7-layer verification pipeline including RFC syntax validation, DNS/MX record verification, real-time SMTP handshakes, and mailbox checks. Combined with our 1M+ disposable domain database and toxic domain filtering, we achieve 98.5%+ accuracy.
Do you store my email lists?
Absolutely not. We enforce a strict Zero-Retention Policy. Your files are processed in volatile RAM and deleted immediately after you download your results. We never log, store, or resell your contact data.
What file formats do you support?
We support .CSV, .XLS, and .XLSX files. Our parser automatically detects the email column regardless of how it is labeled, and preserves all sheets in multi-tab Excel workbooks.
What makes your cleaning more complete than competitors?
Beyond basic syntax and MX checks, we include a 1M+ disposable email database, toxic domain blocking, spam pattern detection, role-based account flagging, catch-all identification, greylisting-aware retries, and multi-sheet Excel preservation.
Why are some emails marked "Unknown"—and am I charged?
Some corporate mail servers block external verification attempts or return ambiguous responses. Rather than guessing, we mark them as "Unknown" and never charge credits for Unknown or Duplicate rows ($0).
What are disposable emails and why remove them?
Disposable emails are temporary burner addresses (Temp-Mail, Guerrilla Mail, 10MinuteMail) that expire in minutes and have zero commercial value. Our database tracks over 1 million disposable domains to keep fake signups out of your CRM.
How does multi-sheet Excel preservation work?
Upload an Excel workbook with multiple tabs (e.g., `Contacts`, `Sales`, `Accounts`) and our Cleaned Database export preserves every tab with its original name and formatting while removing invalid emails from the contact sheet.
What is the difference between hard bounce and soft bounce?
Hard bounces are permanent delivery failures (non-existent mailbox, dead domain) that must be removed immediately. Soft bounces are temporary issues (full inbox, server busy). We clearly separate both in your report.
Will this work with my ESP or CRM?
Yes. Cleaned CSV and Excel files import directly into HubSpot, Mailchimp, Klaviyo, SendGrid, ActiveCampaign, Instantly, Smartlead, and any other ESP or outreach platform.
How fast is bulk verification?
Our parallel engine verifies typical lists in seconds to a few minutes. Larger lists (50k+ rows) are processed asynchronously with live progress updates so you can download your cleaned file as soon as it finishes.
Is KaijuVerifier GDPR compliant?
Yes. Because all verification runs in volatile memory with zero disk retention and TLS 1.3 encryption in transit, KaijuVerifier is designed from the ground up for EU/GDPR data minimization and privacy compliance.