Email Validator: Syntax and Domain-Level Checks
Our email validator checks whether an address is correctly formed and whether its domain can receive mail at all. It validates syntax, looks up MX records, flags disposable providers, identifies role-based addresses, and tells you whether the domain is a free consumer provider. That catches the majority of junk in a signup list — typos, dead domains and throwaway addresses.
Email validation matters for marketers, sales teams, and anyone who collects addresses. Invalid emails cause bounces, hurt sender reputation, and waste resources. These are domain-level signals, which is a genuine limit worth understanding before you rely on them — see the section below.
What We Check
Syntax Validation: Checks if the email follows the correct format ([email protected]).
MX Record Check: Verifies the domain has mail servers configured to receive email, and lists them in priority order.
Implicit MX Fallback: If there is no MX record, checks for an A record, which RFC 5321 treats as an implicit mail host.
Disposable Detection: Identifies known temporary email services like Mailinator and Guerrilla Mail.
Role-Based Detection: Flags generic addresses like info@, support@, admin@.
Free Provider: Indicates if the address is from Gmail, Yahoo, Outlook, etc.
What We Do Not Check
There is no SMTP mailbox probe. We do not connect to the mail server and ask whether a specific inbox exists — not on any tier, and not as a paid extra. Two reasons. First, it is unreliable: most large providers accept every address at the SMTP layer and bounce later, so a "mailbox exists" result from a catch-all or a major provider means very little. Second, probing strangers' mail servers to enumerate addresses is the same technique list-scrapers use, and it gets the prober's IP blocklisted.
We also do not check SPF, DKIM or DMARC records, and we do not detect catch-all configuration. So read a positive result as "this address is well-formed and its domain accepts mail" — not as proof that a person is behind it. The only way to confirm a mailbox truly exists is to send it something, which is what a double opt-in confirmation is for.
Why Email Validation Matters
Reduce Bounces: High bounce rates damage your sender reputation.
Improve Deliverability: Clean lists have better inbox placement rates.
Save Money: Don't pay to send to invalid addresses.
Prevent Fraud: Disposable emails are often used for abuse.
Better Analytics: Accurate lists mean accurate metrics.
Email Types Explained
Free Provider: Gmail, Yahoo, etc. Common for B2C but may indicate lower intent for B2B.
Disposable: Temporary emails that expire. Often used for sign-ups without intent to engage.
Role-Based: Generic departmental emails (info@, support@). Typically managed by teams, not individuals.
Catch-All: Domains configured to accept any email. We do not detect these, and they are the main reason mailbox-level verification is unreliable everywhere.
FAQ
How accurate is email validation?
The syntax and MX checks are close to 100% accurate at what they measure: whether the address is well-formed and whether the domain has somewhere to deliver mail. They cannot tell you the mailbox exists. Expect this to remove typos, dead domains and disposables from a list — not to guarantee delivery to any individual address.
Does the premium plan add SMTP verification?
No. There is no premium plan on ZipConvert right now — subscriptions are on hold and every tool is free for everyone — and mailbox probing is not something we do at any tier. Nothing on this page is withheld pending an upgrade.
Can I validate a whole list at once?
Up to 25 addresses per batch, using the Bulk Validation tab — paste one address per line and export the results as CSV. Anything beyond the first 25 is ignored, and the tool tells you so; the cap exists because each address is a separate DNS lookup and the endpoint is rate limited per minute. For cleaning a list of thousands, a dedicated list-hygiene service is the right tool.
Should I remove all role-based emails?
Not necessarily. Role-based emails are legitimate for business contact but may have lower engagement. Consider your use case—they're fine for transactional emails but risky for marketing campaigns.