Email list health check
Drop in a CSV of up to 5,000 rows and this tool finds duplicates, invalid syntax, misspelled domains, disposable and role addresses, and domains that cannot receive mail. It runs in your browser, is free and needs no signup. It does not check whether mailboxes exist; that takes an SMTP check.
Drop a CSV here, or
CSV or plain text, up to 5,000 rows
Your list is processed in your browser. Only the domain names (the part after the @) are sent to our server for the disposable and MX checks, and they are not stored.
Every address left after the free check still need a mailbox check.
This tool removed what can be found without contacting a mail server. Whether each remaining mailbox actually exists can only be answered by asking the server that hosts it — an SMTP check — and that is what the paid plan does.
- Upload the cleaned file as it is — CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Valid, risky and invalid exported as separate files
One plan, cancel anytime, no contract. The free tools stay free and unmetered either way — they are not a trial.
How it works
- Your file is parsed in the browser. The email column is picked automatically from the content, and you can change it if the guess is wrong. Quoted fields, semicolon or tab separators and Excel’s byte-order mark are all handled.
- Text checks run locally. Syntax, exact duplicates (ignoring case), Gmail duplicates that differ only by dots or a +tag, role prefixes such as postmaster@ and noreply@, and common misspellings like gmial.com, each with the corrected address suggested.
- Only domains go to the server. Each unique domain is checked against 8,740 known disposable providers and looked up in DNS for an MX record, a null MX, or an A record to fall back on. No mail server is contacted and nothing is stored.
- You download two files. A cleaned CSV with every problem row removed and your original columns intact, and a CSV of the problem rows with the reason for each, so nothing disappears without explanation.
What this check cannot tell you
Every row left in your cleaned file has correct syntax and a domain that can receive mail. That says nothing about whether the mailbox itself exists. A person who left the company last year has a perfectly formed address on a perfectly working domain, and it will hard-bounce. The only way to find out is to ask the receiving mail server, which is an SMTP check, and this tool deliberately never does that.
For the full sequence, from suppression lists through to bounce handling, see how to clean an email list. To do the same steps in a spreadsheet or a short script, see how to remove invalid and duplicate emails from a CSV. To check a single domain by hand, use the disposable email checker.
Common questions
- Does this tool check whether email addresses exist?
- No. It finds the problems that can be detected without contacting a mail server: bad syntax, duplicates, misspelled domains, disposable providers, role addresses and domains that cannot receive mail. Whether a specific mailbox exists can only be answered by the server that hosts it, through an SMTP check, which this free tool never performs.
- Is my email list uploaded to your server?
- No. The file is read and checked in your browser. The only thing sent to our server is the list of unique domain names, such as gmail.com or yourcompany.com, so we can look up MX records and compare them against the disposable list. Full addresses never leave your device, and the domains are not stored.
- What counts as a dead domain?
- A domain with no mail server at all (no MX record and no A record to fall back on), a domain that does not exist, or one that publishes a null MX record, which is an explicit statement that it accepts no mail. A domain that only has an A record still counts as able to receive, because mail servers fall back to it.
- Why does Gmail count dotted addresses as duplicates?
- Gmail ignores dots in the part before the @ and anything after a plus sign, and googlemail.com delivers to the same inbox. So j.smith+news@gmail.com and jsmith@googlemail.com reach one person. Sending to both means that person gets your email twice, which is a common route to a spam complaint.
When the cleaned file is ready for mailbox verification, see pricing for what SimpleVerifier checks and the published limits.