Verify any email address in seconds - SMTP handshake, MX records, catch-all detection, disposable check, and ML scoring. No account needed.
5-stage pipeline - 65+ signals per email - 99.8% accuracy - 200+ mail providers
BounceZero Research
Across our verification network, 12.3% of addresses are already dead - roughly one in eight bounces the moment you send. And a clean list decays fast: of addresses verified valid, only 19% are still valid when re-checked past 90 days. Verifying once and reusing the result for a quarter is close to not verifying at all.
Read the full deliverability research Source: BounceZero Deliverability Benchmarks 2026, snapshot Q3-2026.
BounceZero runs five stages in sequence. Each stage eliminates uncertainty and adds confidence to the final verdict.
Validates RFC 5321 format, detects role addresses (info@, noreply@), and checks for common typo patterns before making any network call.
Resolves the domain's DNS, checks MX records exist and point to live mail servers, and fingerprints the provider (Gmail, Outlook, Yahoo, corporate).
Opens a connection to the mail server and issues RCPT TO - the same signal a real email would trigger - without delivering a message.
Sends 3 random addresses to detect domains that accept everything. Catch-all domains are probed individually against the provider to resolve them; any that stay unresolved are flagged rather than mislabelled.
When SMTP probing is blocked (Gmail, some corporate), an XGBoost + Bayesian model scores deliverability based on 65+ historical and contextual signals.
Every verified email gets one of two verdicts, a 0-100 confidence score, and a plain-English explanation.
The mailbox passed verification and is deliverable. Safe to send to. Score typically 75-100.
The mailbox was not verified as deliverable - it may not exist, be disposable, or could not be confirmed. Do not send.
Checks that the email address is correctly formatted - right syntax, valid TLD, no forbidden characters. Fast (under 1ms), offline, no network calls.
Confirms the email address actually exists and can receive mail. Connects to the real mail server. Takes 2-8 seconds but is definitive.
BounceZero does both - validation is stage 1, SMTP verification is stages 2-5. You get a complete picture in a single API call.
The free tool above is for single-address spot checks. For bulk list cleaning, use BounceZero's full platform - upload a CSV of up to 10 million rows, connect via REST API, or set up real-time verification at your sign-up form.
An email verifier is a tool that confirms whether an email address exists and can receive messages. It works by checking the address syntax, resolving the domain's MX records, opening an SMTP connection to the mail server, and probing whether the specific mailbox accepts delivery - all without sending an actual email.
Email verification runs in five stages: (1) Syntax - validates format against RFC 5321. (2) Domain/MX - confirms working mail servers exist. (3) SMTP handshake - issues a RCPT TO command to test the mailbox. (4) Catch-all probe - detects domains that accept all addresses. (5) ML scoring - estimates deliverability when SMTP probing is blocked (e.g. Gmail).
Not exactly. Email validation means checking the format (syntax) only. Email verification goes further - it connects to the actual mail server and confirms the mailbox exists. BounceZero does both: validates format first, then verifies deliverability via SMTP and machine learning.
Yes. For Outlook, Yahoo, and corporate domains, BounceZero uses direct SMTP probing - highly accurate. For Gmail, Google blocks external SMTP probes, so BounceZero applies an ML model trained on millions of outcomes. Gmail results include a confidence score so you know exactly how certain the result is.
You can verify 3 email addresses per session without an account. Create a free BounceZero account to get 100 verifications per month - no credit card required. Bulk verification starts at $3 per 1,000 and credits never expire.
Valid: the mailbox passed verification and is deliverable - safe to send. Invalid: the mailbox was not verified as deliverable - it may not exist, be disposable, or could not be confirmed. The 0-100 score shows how confident we are in the verdict.
No credit card. No expiry. Just accurate results from a 5-stage pipeline used by 2,400+ marketers and developers.
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