Help Center

Yes! During our beta period, enjoy unlimited email verifications completely free. No credit card, no trial period limitations, no hidden fees. After beta, we'll offer 10,000 free verifications per month, then $0.47 per 1,000 emails - the best price in the industry.

No account needed during beta! Simply visit the homepage, upload your file, and start verifying. For post-beta API access and advanced features, we'll offer optional accounts with usage tracking and team collaboration.

We support .CSV, .XLS, and .XLSX files. Maximum file size is 50MB. Our intelligent system automatically detects which column contains emails, regardless of the column name ("Email", "E-mail", "Contact", etc.).

We achieve 98%+ accuracy through our comprehensive multi-layer approach: syntax validation (RFC 5322 compliance), DNS/MX record verification, real-time SMTP handshakes, mailbox verification, plus advanced filtering for disposable domains (1M+ database), toxic domains, and spam patterns. This is significantly more thorough than most competitors who only check syntax and DNS.

Most verifiers perform basic syntax and DNS checks. Kaiju goes much further with: 1 million+ disposable email domains (Temp-Mail, Guerrilla Mail, etc.), toxic domain blocking (spam/fraud sources), spam word filtering, role-based detection (info@, sales@), catch-all detection, greylisting awareness, and industry-first multi-sheet Excel preservation. No competitor offers this comprehensive filtering arsenal.

Certain mail servers (Yahoo, AOL, corporate domains) block verification attempts or return ambiguous responses for privacy/security. Rather than guessing and risking false positives, we mark these as "Unknown". You can decide whether to keep or remove them based on your email strategy and risk tolerance. Conservative approach: remove them. Aggressive approach: keep them with monitoring.

Hard bounces are permanent delivery failures: non-existent mailbox, invalid domain, or deleted accounts. These MUST be removed immediately to protect sender reputation. Soft bounces are temporary: full mailbox, server temporarily down, message too large. These may succeed later. We identify both clearly so you can make informed decisions.

This is an industry-first exclusive feature. Upload an Excel workbook with multiple sheets (e.g., Contacts, Sales Data, Inventory) and our "Cleaned Database" download preserves ALL sheets with original names and data. We only clean invalid emails from the sheet containing the email column - all other sheets remain completely untouched. No other email verifier offers this capability.

Disposable (temporary) emails are created through services like Temp-Mail, Guerrilla Mail, 10MinuteMail, Mailinator, etc. Users create them to avoid giving real addresses. These addresses expire quickly (minutes to hours) and have ZERO long-term engagement value. Our 1 million+ domain database catches these automatically. Keeping them wastes money and damages list quality.

Toxic domains are those associated with spam complaints, fraud, malicious activity, or abuse. Sending to these addresses damages your sender reputation and may get you blacklisted by ISPs. We maintain a curated blocklist of these domains and automatically flag them for removal.

Catch-all (accept-all) domains are configured to accept emails to ANY address @domain.com, even if the mailbox doesn't exist. For example, randomtext123@catchalldomain.com will appear to pass verification, but the email might not actually be delivered. We detect these so you can decide whether to risk including them.

Absolutely NOT. We have a strict Zero Retention Policy. Your files are processed entirely in-memory (RAM) and automatically deleted immediately after you download the results. We never log, store, archive, or access your data. Files in our temp folder are deleted within 1 hour maximum. Your privacy is 100% guaranteed.

Yes. Our zero retention policy ensures we don't process or store personal data beyond the immediate verification session. Email verification itself helps with GDPR compliance by ensuring you only email valid, reachable addresses. Our role-based email detection helps identify addresses that may not meet consent requirements. However, verification alone doesn't guarantee full GDPR compliance - you still need proper consent mechanisms and privacy policies.

Our parallel processing engine verifies emails at high speed with concurrent SMTP connections. Small lists (under 1,000): typically 30 seconds to 2 minutes. Medium lists (1,000-10,000): 2-10 minutes. Large lists (50,000+): 20-60 minutes depending on SMTP rate limiting from recipient servers. We're significantly faster than competitors due to optimized infrastructure.

Yes! Our cleaned lists work with ALL email platforms: Mailchimp, SendGrid, Constant Contact, ActiveCampaign, HubSpot, Klaviyo, Sendinblue, MailerLite, ConvertKit, GetResponse, AWeber, and any other ESP or CRM. Simply export your list, clean with Kaiju, then re-import. Since most ESPs charge by subscriber count, cleaning reduces your monthly costs.

If you close your browser or lose connection during verification, the process will stop and results will be lost. During beta, simply re-upload and start again (it's free). Post-beta, we'll add session recovery features for paid users to resume interrupted verifications.