Email List Cleaner
Clean and validate email lists. Remove duplicates, normalize casing, validate RFC 5322 format, and export cleaned lists. All processing happens locally in your browser — no data uploaded to servers.
100% Client-Side Processing
Your email lists are processed entirely in your browser. No data is sent to any server. This tool does not verify email deliverability (no SMTP verification) — it only validates format according to RFC 5322 standards.
Cleaning Options
Accepts plain text (one email per line) or CSV format (email as first column). Empty lines are automatically skipped.
Table of Contents
What is Email List Cleaning?
**Email list cleaning** is the process of removing invalid, duplicate, and malformed email addresses from your email list. It ensures your list contains only valid, unique email addresses that follow the RFC 5322 email format standard.
A clean email list is essential for:
- Email marketing campaigns — Higher deliverability and lower bounce rates
- Newsletter management — Maintain a healthy subscriber list
- Data quality — Ensure your customer database is accurate
- Cost savings — Avoid paying for invalid or duplicate email addresses in email service providers
- Compliance — Maintain clean lists for GDPR and CAN-SPAM compliance
Our Email List Cleaner processes your list entirely in your browser — no data is uploaded to servers. It validates format according to RFC 5322 standards (but does not verify actual deliverability via SMTP).
Features
Remove Duplicates
Automatically identifies and removes duplicate email addresses from your list. Case-insensitive
duplicate detection ensures that User@Example.com and user@example.com are recognized as the same address.
The tool shows you exactly how many duplicates were found and removed, giving you full transparency into the cleaning process.
Normalize Casing
Converts all email addresses to lowercase for consistency. While email addresses are case-insensitive according to RFC standards, normalizing to lowercase ensures uniformity across your list and prevents issues with some email systems.
You can toggle this feature on or off depending on your needs.
RFC 5322 Format Validation
Validates email addresses against RFC 5322 format standards, ensuring they have:
- Valid local part (before @) — max 64 characters, no consecutive dots
- Valid domain part (after @) — max 255 characters, includes TLD
- Proper @ symbol placement
- Total length within 254 characters
- Allowed characters according to RFC 5322
Invalid emails are identified and can be automatically removed or kept for review.
Export Cleaned List
Easily export your cleaned email list in multiple ways:
- Copy to clipboard — One-click copy for quick use
- Download as TXT — Save cleaned list as a text file
The exported list is ready to import into your email marketing platform, CRM, or other tools.
How it Works
The Email List Cleaner processes your list through several stages:
1. Input Parsing
Your email list can be provided in two formats:
- Plain text — One email address per line
- CSV format — Email address as the first column
Empty lines are automatically skipped, and the tool handles both Windows (\r\n) and
Unix (\n) line endings.
2. Normalization
If enabled, all email addresses are converted to lowercase and trimmed of whitespace. This ensures consistency and helps with duplicate detection.
3. Format Validation
Each email is validated against RFC 5322 format standards. The validation checks:
- Presence and proper placement of @ symbol
- Local part length and character restrictions
- Domain part structure and TLD presence
- Total email length limits
- Character validity according to RFC 5322
4. Duplicate Detection
Case-insensitive duplicate detection identifies emails that appear multiple times in your list. If enabled, duplicates are removed, keeping only the first occurrence.
5. Export
The cleaned list is ready to copy or download. All processing happens instantly in your browser — no waiting for server processing.
RFC Format Validation
Our tool validates email addresses according to **RFC 5322** (Internet Message Format) standards. This ensures emails follow the proper format, but important limitations apply:
⚠️ Format Validation Only
This tool validates email format only. It does not verify:
- Actual deliverability (SMTP verification)
- Whether the email address exists
- Whether the domain is active
- Whether the mailbox accepts messages
- Disposable/temporary email detection
For full deliverability verification, you'll need to use specialized email verification services that perform SMTP checks. This tool focuses on format-level validation and cleaning.
Valid email formats according to RFC 5322 include:
user@example.com— Standard formatuser.name@example.com— With dot in local partuser+tag@example.com— With plus signuser_name@example.com— With underscoreuser123@example.com— With numbers
Invalid formats include:
@example.com— Missing local partuser@— Missing domainuser..name@example.com— Consecutive dotsuser@example— Missing TLDuser example.com— Missing @ symbol
Common Use Cases
- Email Marketing: Clean subscriber lists before sending campaigns to improve deliverability and reduce bounce rates
- CRM Data Management: Validate and clean email addresses in customer databases to maintain data quality
- Lead Generation: Clean email lists collected from forms, events, or lead sources
- Newsletter Management: Remove duplicates and invalid addresses from newsletter subscription lists
- Data Migration: Prepare email lists for import into new systems or platforms
- Compliance: Ensure email lists meet data quality standards for GDPR and CAN-SPAM compliance
- Cost Optimization: Remove invalid and duplicate emails to reduce costs in pay-per-email marketing services
- Merge Lists: Clean combined email lists from multiple sources to remove duplicates
Frequently Asked Questions
No. This tool only validates email format according to RFC 5322 standards. It does not perform SMTP verification or check if email addresses actually exist or can receive messages. For deliverability verification, you'll need specialized email verification services.
Yes. All processing happens entirely in your browser — no data is uploaded to any server. Your email lists never leave your device. This makes it safe for sensitive customer data, GDPR compliance, and privacy-critical use cases.
You can paste email lists directly as text (one per line) or upload TXT, CSV, or TSV files. If uploading a CSV/TSV file, the tool automatically extracts the email from the first column. All line endings (Windows, Unix, Mac) are supported.
Duplicates are detected case-insensitively, so User@Example.com and user@example.com are considered the same email. The tool keeps the first
occurrence and removes subsequent duplicates. If normalization is enabled, all emails are
converted to lowercase before duplicate detection.
Invalid emails are identified and can be automatically removed (if "Remove invalid emails" is enabled) or kept in the list for review. The tool shows you which emails are invalid and why, making it easy to fix issues manually if needed.
The tool works entirely in your browser, so performance depends on your device. It can handle lists with thousands of emails, but very large lists (100,000+ emails) may take longer to process. For optimal performance, consider processing large lists in batches.
No. According to RFC standards, email addresses are case-insensitive. Normalizing to lowercase doesn't affect deliverability and is a best practice for consistency. Some email systems recommend lowercase normalization to avoid potential issues.
No. All processing happens locally in your browser. We don't store, save, or transmit any email addresses or data. Your privacy is completely protected.