Web Email Verification Documentation

Getting Started

Kaiju Email Verifier is designed to be the simplest yet most powerful email cleaning solution. Verify single emails or run an instant bulk CSV/Excel pre-scan right in your browser, with 100 free monthly checks and never-expiring credit packs from $19.

Quick Start (3 steps)

1. Visit the homepage at kaijuverifier.com
2. Upload your file by dragging and dropping or clicking "Browse Files"
3. Download results once verification completes (typically within minutes)

File Upload Guide

Supported File Formats

• .CSV (Comma-Separated Values) - Most compatible
• .XLS (Excel 97-2003) - Legacy Excel format
• .XLSX (Excel 2007+) - Modern Excel format with multi-sheet support

File Requirements

• Maximum size: 50MB per file
• Headers required: First row should contain column names
• Email column: Will be auto-detected (works with "Email", "E-mail", "Contact", etc.)
• Character encoding: UTF-8 recommended for international characters

Multi-Sheet Excel Files

Industry-First Feature: Unlike any other email verifier, Kaiju preserves ALL sheets in your Excel workbook.

Example: You have a workbook with 3 sheets:

• Sheet 1 "Customers": Name, Email, Phone → Email column gets cleaned
• Sheet 2 "Sales": Product, Revenue, Date → Remains completely unchanged
• Sheet 3 "Inventory": SKU, Stock, Location → Remains completely unchanged

Understanding Verification Results

Result Categories

✓ Valid Emails

Emails that passed all verification layers:

• Correct syntax (RFC 5322 compliant)
• Valid domain with MX records
• SMTP server accepts the mailbox
• NOT disposable/temporary
• NOT on toxic domain list
• No spam patterns detected

Action: Safe to send emails. These are your high-quality subscribers.

✗ Invalid Emails - Detailed Categories

Syntax Errors:

• Missing @ symbol or domain
• Invalid characters
• Malformed structure

DNS/Domain Issues:

• Domain doesn't exist (NXDOMAIN)
• No MX records configured
• Domain expired or parked

SMTP Failures:

• Mailbox doesn't exist (hard bounce)
• Account disabled or deleted
• Mail server explicitly rejects address

Disposable/Temporary Emails:

• Detected in our 1 million+ disposable domains database
• Examples: Temp-Mail, Guerrilla Mail, 10MinuteMail, Mailinator, etc.
• These expire quickly (minutes to days)

Toxic Domains:

• Known spam complaint sources
• Fraud/abuse history
• ISP blacklist entries

Spam Patterns:

• Bot-generated addresses
• Common spam keywords
• Suspicious character sequences

Action: REMOVE these immediately. Keeping them damages sender reputation and wastes money.

⚠ Unknown Emails

Emails where verification couldn't be conclusively determined:

• Greylisting: Server temporarily delays verification (anti-spam measure)
• Catch-All Domains: Accept emails to any address @domain.com
• Privacy Blocking: Yahoo, AOL, some corporate servers block verification
• Server Timeout: SMTP server didn't respond in time

Download Options

Three Download Types

1. Clean List (filename_clean.xlsx)

Contains only the valid emails. This is your safe-to-send list.

• Columns: Email, Status: "Valid"
• Use this for: Email campaigns, marketing automation, CRM import

2. Invalid Report (filename_invalid.xlsx)

Contains all invalid and risky emails with detailed reasons.

• Columns: Email, Status: "Invalid", Reason (specific issue identified)
• Use this for: Understanding list quality, identifying data collection problems

3. Cleaned Database (filename_cleaned_database.xlsx)

Most powerful option: Your original file with invalid emails removed.

• Preserves ALL columns from original file
• Multi-sheet support: All sheets preserved with original names
• Only the email column is cleaned (invalid emails removed)
• Use this for: Updating your CRM/database while maintaining all data

Best Practices

How Often Should I Clean My Lists?

• New lists: ALWAYS verify before first send
• Active lists: Every 3-6 months minimum
• Inactive subscribers: Verify before re-engagement campaigns
• Post-purchase: Clean immediately after buying or scraping lists
• High bounce rate (>5%): Clean immediately

List Hygiene Tips

1. Remove duplicates first: De-duplicate before verification to save resources
2. Separate domains: Large clients (Gmail, Yahoo) vs. corporate domains
3. Monitor engagement: Even verified emails can become inactive over time
4. Use double opt-in: Reduce invalid signups at the source
5. Regular cleaning: Set calendar reminders for quarterly verification

Integration with Email Service Providers

Works seamlessly with all major platforms:

• Step 1: Export list from your ESP (Mailchimp, SendGrid, etc.)
• Step 2: Upload to Kaiju and verify
• Step 3: Download "Cleaned Database"
• Step 4: Re-import to your ESP (update existing contacts or create new segment)

Handling Unknown Results

Strategy based on your situation:

Scenario	Recommendation
Cold outreach / New lists	Remove unknowns - Maximize deliverability
Existing engaged subscribers	Keep unknowns - Likely real users
Poor sender reputation	Remove unknowns - Rebuild trust
Strong sender reputation	Test segment - Send to small batch first

What Makes Kaiju's Cleaning Complete

Verification Layers (Most Comprehensive in Industry)

Layer 1: Syntax Validation

RFC 5322 compliance check. Identifies malformed addresses, missing domains, invalid characters.

Layer 2: DNS/MX Validation

Verifies domain exists and has mail servers configured to receive emails.

Layer 3: SMTP Handshake

Real-time connection to mail server. Confirms mailbox existence without sending emails.

Layer 4: Mailbox Verification

Ensures specific mailbox is active, not full, and can receive messages.

Layer 5: Disposable Detection (1M+ Database)

Cross-references against our continuously updated database of over 1 million disposable email domains.

Layer 6: Toxic Domain Blocking

Identifies domains with spam complaint history, fraud activity, or ISP blacklist entries.

Layer 7: Spam Pattern Detection

AI-powered detection of bot-generated addresses and suspicious patterns.

Layer 8: Role-Based Detection

Flags generic addresses (info@, sales@, support@) that often have low engagement.

Layer 9: Catch-All Detection

Identifies domains that accept all emails, flagging uncertain deliverability.

Layer 10: Greylisting Awareness

Smart handling of anti-spam delays to prevent false negatives.

Database Sizes (Industry-Leading)

• Disposable Domains: 1,000,000+ entries (updated weekly)
• Toxic Domains: Curated list of known spam/fraud sources
• Spam Patterns: Machine learning model trained on millions of addresses