Email Validator — RFC 5322 Syntax + DNS MX Record Check (Free)
Validate email addresses against RFC 5322 syntax + check the domain MX records exist. Bulk check up to 1,000 emails. Free.
About Email Validator
An email validator checks whether a string is a syntactically valid email address per RFC 5322, whether the domain part has functioning DNS MX (mail-exchange) records, and optionally whether the address looks like a disposable / role-based / typo-prone variant — useful before sending to a list, for form validation, and for cleaning a stale CRM. The ZTools Email Validator runs the syntax check in the browser and uses a public DNS-over-HTTPS resolver for MX checks, supports bulk validation of up to 1,000 addresses, exports labelled results to CSV / JSON, and never sends a real email so it does not poison delivery reputation.
Use cases
- Form input validation. Frontend forms accept whatever users type; "user@gmial.com" passes naive regex but is wrong. Run the typo-detector to catch the most common mistakes before submit.
- CRM list cleanup. A 2-year-old CRM list has stale addresses. Bulk-validate; flag domains with no MX (likely dead) for soft-suppression before the next campaign.
- Disposable-email blocking. Sign-up form should reject Mailinator / 10minutemail / etc. The validator detects ~3000 known disposable domains.
- Pre-import data cleaning. CSV import of contacts. Run validation first; quarantine the invalid ones for human review rather than letting them clog the database.
How it works
- Paste email(s). Single address or one-per-line for bulk. Up to 1,000 per batch.
- Syntax check. RFC 5322 regex covering local-part rules, quoted strings, IP-literal domains, internationalised (IDN) addresses.
- MX DNS check. Public DNS-over-HTTPS lookup (Cloudflare 1.1.1.1) confirms the domain has at least one mail-exchange record.
- Heuristic flags. Disposable-domain match, role-based (info@, support@), typo suspicion (gmial.com, yaho.com, hotnail.com).
- Export results. CSV columns: email, syntax_valid, mx_valid, disposable, role, typo_suggestion.
Examples
Input: user@example.com
Output: syntax_valid=true, mx_valid=true, disposable=false, role=false
Input: user@gmial.com
Output: syntax_valid=true, mx_valid=false, typo_suggestion=user@gmail.com
Input: admin@example.com
Output: syntax_valid=true, mx_valid=true, role=true
Frequently asked questions
Does it actually send a probe email?
No — and that is the correct design. Sending probe emails harms sender reputation. We rely on syntax + MX + heuristics, which together catch ~95% of invalid addresses.
How accurate is MX-based validation?
A valid MX confirms the domain accepts mail. It does NOT confirm the specific mailbox exists — only the domain itself accepts delivery. SMTP-level mailbox probes are unreliable and often blocked, so we skip them.
What is a role-based address?
Generic mailboxes like info@, support@, admin@, sales@. ESPs sometimes block these to protect engagement metrics. The flag lets you choose.
Are international (Unicode) emails supported?
Yes — ümlaut@example.com and 用户@例子.com pass syntax. MX check still applies to the punycode-encoded domain.
How are typos detected?
Levenshtein distance + a curated list of common provider domains (gmail, yahoo, hotmail, outlook, icloud). Distance ≤ 2 with a known target produces a suggestion.
Is the data stored or sent anywhere?
Only DNS lookups go to Cloudflare's public 1.1.1.1 resolver — that is required for MX checks. The address strings themselves are not stored.
Pro tips
- On signup forms, run typo detection — converting "gmial" → "gmail" recovers a real user before they bounce.
- For CRM cleanup, soft-suppress (mark, do not delete) MX-failed addresses; manual review may catch a temporary DNS outage.
- Treat disposable-domain flag as advisory — some legit users use them; block only if abuse is real.
- Always validate at signup AND before send. Domains die between those moments.
- Never validate by sending a real email — bounce rate kills sender reputation.
Reviewed by Ahsan Mahmood · Last updated 2026-05-05 · Part of ZTools.
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