DFY GTM Systems

Free Email List Validator Check Email Syntax & Domain MX Records

Paste your list and get two layers of validation: RFC-style syntax per email, plus a live DNS lookup confirming each domain actually accepts mail (MX records). Domains with no MX records are near-certain hard bounces.

How this check works

  1. 01

    Every email is syntax-checked locally.

  2. 02

    Unique domains are extracted and queried over DNS-over-HTTPS for MX records (up to 25 domains per run).

  3. 03

    Emails are bucketed into valid, risky (domain has no MX), and invalid syntax.

  4. 04

    Results include a per-domain MX table so you can see exactly which domains fail.

How to fix common problems

Domains with no MX records

Remove these addresses sending to them produces hard bounces, and more than ~2% hard bounce rate damages sender reputation.

Catch-all domains

Some domains accept everything. MX alone cannot detect catch-alls; for those, use a paid verification pass or send small test batches first.

Example

Of 200 emails across 140 domains, 9 domains return no MX record → those 14 addresses are dropped, saving a 7% bounce hit.

FAQ

Is this as accurate as paid verifiers?
MX validation catches dead domains the biggest bounce source. Paid tools additionally probe mailboxes (SMTP handshake) and detect catch-alls. Use this first; it's free and instant.
Why the 25-domain limit?
To keep the DNS queries fast and polite. Split very large lists into batches.
Does my list get uploaded?
No. Syntax checks run in your browser; only domain names (not full emails) are sent to a public DNS resolver.

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