Free email validation for cold emailers, agencies and newsletters
Clean your email list before it burns your domain
List Desk is a free email list validator by Przemysław Zalewski, an independent engineer. It flags dead domains, typos, disposable and role addresses before they turn into hard bounces. Addresses stay in your browser.
Is your sending domain ready?
A clean list is half the job. The other half is SPF, DKIM and DMARC on the domain you send from.
What is checked
Syntax and duplicates
Practical address syntax, and duplicates including Gmail dots and +tags, which land in the same mailbox.
The domain accepts mail
Each unique domain is looked up in DNS: MX records, a null MX that refuses all mail (RFC 7505), the A-record fallback (RFC 5321) and domains that do not exist.
Disposable, typos, roles
Over 9,900 disposable domains (public CC0 list), typo fixes for popular providers (gmial.com → gmail.com), and role accounts such as info@ that complain more often.
What it does not check yet
Whether a specific mailbox exists. That needs a short SMTP conversation with the recipient’s server from a server with a good reputation, which is the next step of this tool. Leave your email and I will tell you when it is ready.
Compared with SMTP verifiers (ZeroBounce, NeverBounce): List Desk does not probe mailboxes yet; it checks syntax, DNS, disposable providers and typos and keeps addresses in your browser. For list cleaning before a campaign that already removes a lot; for full email verification of each mailbox, those services go further today. What each one checks, side by side.
Your list stays with you
- The file is read in your browser. Addresses are never sent to the server; only the unique domains are, to look them up in DNS.
- Domain results are cached for a day so repeated checks are fast. A daily counter of checked domains per network (hashed IP) is kept for 3 days to enforce the free limit; nothing else is stored.
- Analytics records only counts (how many rows, how many removed), never addresses or domains.
Sending at volume? Make every send follow the rules
List hygiene is one part. I build the compliance side in your app or platform: one-click unsubscribe (List-Unsubscribe, RFC 8058) as Gmail and Yahoo require, a suppression list every send checks, hard bounces and spam complaints recorded from your provider, and SPF, DKIM and DMARC aligned. I built and ran a mail product that sent millions of messages.
I reply within 24 hours on working days, personally. If I am late, the first hour of work is free.
Questions
Is it really free?
Yes, up to 50,000 addresses per check and 20,000 unique domains a day. It is how I show what I build.
Why not check every mailbox now?
Mailbox checks need an SMTP conversation on port 25 from a server with a clean reputation, which cloud platforms block by default. It is coming as the next step; the checks here already catch many hard bounces before they happen, such as dead domains and typos.
Email validation or email verification: what is the difference?
Validation checks that an address can work: syntax, a domain that accepts mail, no disposable provider, no typo. Verification also asks the recipient’s server whether the mailbox exists. List Desk does validation and list cleaning now; mailbox verification is the next step.
What should I do with "Risky" addresses?
Role addresses (info@, sales@) and free mailboxes are valid but complain more on cold email. Send to them carefully, in smaller batches, or leave them out of cold campaigns.
Is my list uploaded anywhere?
No. Open the browser network tab while it runs: only lists of domains are sent.
The list is clean, but my emails still land in spam. What next?
Test the email itself: send one campaign email to the free Email Test. It checks one-click unsubscribe, SPF, DKIM, DMARC and the Gmail and Yahoo rules, and three AI models say how filters and readers see it.
Who built it?
Przemysław Zalewski, an independent engineer. Check your sending domain with the free SPF, DKIM and DMARC checker, your logo in the inbox with the BIMI checker, and make a consistent signature with Signature Desk.
Guides
- A free first pass before you pay ZeroBounce or NeverBounce
What List Desk, ZeroBounce and NeverBounce each check, and when a paid SMTP verifier is the better choice.
