Clean Bulk Email Lists Without Breaking Your Spreadsheets.
Upload large CSV or TXT databases of up to 100,000+ contacts. Eliminate hard bounces and toxic domains before you hit send.
How Bulk Email Verification Works
From raw export to inbox-ready file in under 15 minutes.
Upload Raw Export
Drag & drop any CSV or TXT file from Apollo, LinkedIn, ZoomInfo, or your CRM. We accept files with custom columns, European semicolon delimiters, and messy UTF-8 encoding.
Multi-Threaded Validation
Our distributed engine performs deep RFC syntax checks, DNS records inspection, SMTP mail server handshakes, and spam-trap filtering in parallel threads without rate-limiting.
Download VLOOKUP-Ready File
Export your cleaned file. The email address is moved to Column A for instant formula mapping, while your original row order and custom CRM merge tags remain 100% intact.
Engineered for Spreadsheets & Cold Outreach Stacks
Most bulk verifiers shuffle rows, truncate extra columns, or break character encoding. NullBounce is purpose-built to preserve data integrity:
First Name, Company, or Icebreaker remain intact.What Happens to Every Email in Your List
Our multi-step verification pipeline runs 5 independent security and deliverability checks on every contact before generating your final report.
RFC Syntax & Format Correction
Checks compliant formatting against IETF RFC standards. Strips hidden trailing spaces, detects misplaced special characters
DNS & Live MX Record Audit
Queries domain name servers to verify active Mail Exchange (MX) records. If the company domain has expired, lapsed, or lacks mail servers, the address is instantly flagged as non-deliverable.
Burner & Disposable Domain Detection
Cross-references domains against a continuously maintained database of 50,000+ temporary email providers (e.g. Mailinator, 10MinuteMail) to protect your sender reputation from dead inboxes.
Direct SMTP Mailbox Handshake
Simulates sending a message by pinging the recipient's mail transfer agent (MTA) without actually delivering an email. Confirms whether the individual mailbox exists and can receive incoming mail.
Catch-All & Role Account Isolation
Detects mail servers configured to accept all incoming mail indiscriminately and flags generic role-based addresses (info@, sales@) so you can selectively target high-value leads.
Actionable Statuses. No Confusion.
Every contact receives a clear classification so you know exactly which emails are safe to mail.
Deliverable
Mailbox exists and actively accepts incoming emails. Bounce rate < 1%. Safe for your primary sending domains.
Invalid
Domain does not exist, mailbox is deleted, or address has fatal typos. Delete these to protect your sender score.
Risky
Includes Catch-All domains (servers accepting any username) and Role-Based addresses (e.g., support@, info@). We isolate them so you can choose your risk tolerance.
Unknown
The destination mail server timed out or was temporarily unresponsive. We never charge credits for unknown statuses.
Buy Only What You Need. Down to a Single Lead.
Have a list of 11,350 contacts? Don't pay for 25,000. In NullBounce, you buy the exact number of credits your list requires.
Your Contact Lists Are Safe With Us
Enterprise-grade privacy standards applied to every verification job.
256-Bit SSL Encryption
All file uploads, API requests, and downloads are protected by modern end-to-end TLS encryption.
Auto-Wiped in 30 Days
Uploaded lists and validation results are permanently purged from our servers after 30 days. You can also delete them manually at any time.
Zero Data Sharing
We never sell, rent, or share your proprietary lead lists with third parties. Your data is strictly yours.
No Real Emails Sent
Our engine performs technical DNS and SMTP handshakes, terminating before delivery. Your contacts will never receive test messages.
Bulk Email Verification: Frequently Asked Questions
Everything you need to know about preparing, uploading, and cleaning large email lists.
What file formats and delimiters are supported?
We natively support standard CSV and plain TXT files up to 100,000 rows. Our parser automatically detects comma, semicolon, and tab delimiters, and handles UTF-8 encoding so international characters in contact names are never corrupted.
Do you charge credits for duplicate emails in my list?
No. NullBounce performs automated pre-deduplication before verification begins. If an email appears 10 times in your uploaded CSV, we verify it once and charge only 1 credit. When downloading your cleaned list, you can choose whether to keep or remove the duplicate rows.
How should I handle Catch-All and Risky emails after downloading?
For cold outreach campaigns, we recommend sending exclusively to Safe (Deliverable) contacts to keep bounce rates strictly below 1%. If you must send to Catch-All addresses, segment them into a separate secondary domain with lower sending volume.
Are my uploaded contact lists stored permanently?
No. In strict compliance with GDPR and security best practices, your uploaded files and clean results are automatically and permanently erased from our servers after 30 days. You can also delete them manually in 1 click at any time.
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