Bulk Email List Validation
NullBounce allows you to clean contact lists in bulk. Our multi-threaded verification engine audits DNS records, mailbox existence, and disposable domains while preserving your custom spreadsheet columns and row order.
Supported File Formats & Limits
Section titled “Supported File Formats & Limits”- Supported formats:
.csvand.txt(plain text). - File size limit: up to 50 MB per file.
- Volume limit: up to 100,000 email addresses per single list upload (you can run multiple files in parallel).
Plain Text (.txt) Files
Section titled “Plain Text (.txt) Files”A .txt file must contain only email addresses, strictly one email address per line, with no headers, names, or extra characters like spaces, commas, or semicolons.
Spreadsheet (.csv) Files
Section titled “Spreadsheet (.csv) Files”- Must contain an email column.
- Can include any number of extra columns (e.g.
First Name,Company,Phone,Custom Tags). NullBounce preserves all original columns and row order, returning them in the final report. - Supported delimiters: Comma (
,), Semicolon (;), Colon (:), or Tab.
Single-column .csv file:
| # | Email (Column A) |
|---|---|
| 1 | michael@novalabs.io |
| 2 | billing@stripe.com |
| 3 | support@acme-corp.com |
Multi-column .csv with CRM metadata:
| # | First Name | Company | Custom Tag | |
|---|---|---|---|---|
| 1 | Sarah | Acme Inc | sarah@acme.com | tier_1_lead |
| 2 | Michael | Nova Labs | mike@novalabs.io | inbound_demo |
Free Duplicate Emails Handling
Section titled “Free Duplicate Emails Handling”We never destroy or reorder your contact lists. We keep all rows exactly as they were in your original file.
However, duplicate email addresses are 100% free:
- If an email appears multiple times in your list, our engine validates it once.
- Credits are charged only for unique emails.
You don’t need to manually deduplicate spreadsheets before upload — NullBounce handles it safely and automatically.
Step-by-Step Uploading Process
Section titled “Step-by-Step Uploading Process”1. Upload Your List
Section titled “1. Upload Your List”Log in to your Dashboard, navigate to the Bulk Validation page, and click the Upload List button in the top right corner.
In the opened dialog, select your .csv or .txt file and click Submit:
2. File Preparation & Queue
Section titled “2. File Preparation & Queue”- Your file will briefly appear with the status Preparing while our parser audits delimiters and row syntax.
- Once preparation completes, the status switches to Ready.
- Click Start verification to begin the process.
3. Real-Time Verification Progress
Section titled “3. Real-Time Verification Progress”Once processing begins, you can monitor the live progress bar and status updates in real time:
Aborting a Job:
You can cancel verification at any time by clicking Abort Verification. Verification of unstarted contacts stops immediately. Credits for all unprocessed emails are instantly returned to your balance and will appear on your Payments & Balance History page.
Downloading Validation Results
Section titled “Downloading Validation Results”Once verification finishes, the list status changes to Completed.
Click Download report to export your cleaned .csv file, or click Show statistics to inspect the live breakdown:
File Structure of the Export:
Section titled “File Structure of the Export:”- Email column is moved to Column A so spreadsheet lookup functions (
VLOOKUPorXLOOKUP) work instantly without manual copy-pasting. - Diagnostic columns are added:
RESULT,DELIVERABLE,DISPOSABLE,ROLE,FREE. - All your original columns remain intact: all custom variables, phone numbers, and CRM notes stay in their exact original row sequence.