Sending to an unvalidated list causes hard bounces that damage your ESP reputation - sometimes permanently. Validate first.
Syntax - MX records - SMTP delivery - catch-all detection - disposable email - ML risk scoring
Format alone is not enough. A valid email must pass every layer of the delivery chain.
Passes RFC 5321 syntax check - valid characters, correct structure, no double dots or illegal sequences.
Domain resolves, MX records exist, and the mail server is reachable. Many fake addresses use real-looking but MX-less domains.
The specific mailbox accepts RCPT TO. A domain can have working MX records but individual mailboxes can still be deleted or disabled.
Not catch-all, not disposable, not a role address. Low spam trap probability. BounceZero scores 65+ signals across all these dimensions.
Most forms only check if an email looks right. That misses the majority of invalid addresses.
[email protected] - passes format, fails DNS (`.con` doesn't exist)
[email protected] - passes format, fails SMTP (mailbox deleted)
[email protected] - passes format, is a known disposable provider
[email protected] - passes format and SMTP, but domain accepts everything
DNS resolution confirms domain actually exists with live MX records
SMTP handshake confirms the specific mailbox accepts messages
Disposable provider database of 50,000+ known throwaway domains
3-probe catch-all detection flags domains that accept everything
Passed verification and is deliverable. Safe to send. Confidence score typically above 75.
Not verified as deliverable - it may not exist, be disposable, or could not be confirmed. Do not send.
New to verification? Start with the complete email verification guide.
Email validation is the process of verifying that an email address is correctly formatted, has valid DNS and MX records, and that the mailbox actually exists and can receive messages. It goes far beyond a format check - it tests the full delivery chain before you commit to sending.
The terms are often used interchangeably. Validation typically refers to the full pipeline - format, DNS, MX, SMTP, catch-all, and risk scoring. Verification more specifically refers to the SMTP handshake that confirms the mailbox exists. BounceZero performs both as part of its 5-stage pipeline.
A valid email must: (1) follow RFC 5321 format with no invalid characters, (2) have a domain with live MX records pointing to a reachable mail server, (3) have a mailbox that accepts messages via SMTP, and (4) not be a catch-all, disposable, or role address. BounceZero checks all four plus ML-based risk scoring across 65+ signals.
Email lists decay at roughly 2-3% per month. For active campaigns, validate before every major send. For stored lists, validate quarterly at minimum. The most effective approach is real-time validation at the point of collection using the BounceZero API - invalid addresses never enter your list.
Yes. The free validator above checks individual addresses. For bulk validation, create a free BounceZero account - upload CSV files up to 500K addresses or call the REST API for real-time integration. You get 100 free credits to start, no credit card required, credits never expire.
Upload a CSV or plug in the API. 100 free credits, no card needed - and your first list clean is on us.
Single-email checks, no signup required
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