CSV email verifier: check every address in a CSV file
A CSV email verifier reads the email column of your file and tells you which rows to fix, remove or check. This one finds the column itself, flags bad syntax, duplicates, typo domains, domains with no mail server and disposable addresses, keeps your other columns in the download, and checks the first 10 mailboxes live.
By SimpleVerifier Team · Last updated
How do I verify the emails in a CSV file?
- Drop the CSV file in, or paste its rows. Any delimiter works: comma, semicolon or tab.
- Press Check the CSV. The email column is found by its contents, so a header named
Email AddressorE-mailworks as well asemail. - Read the flagged rows: bad syntax, duplicate, typo domain, no mail server, disposable or role address. Each row says why.
- Download the clean list (all your original columns, flagged rows removed) and the flagged rows for your records.
- Watch the first 10 addresses get a live mailbox check. To check the rest, sign in with Google: your first 100 email checks are free and the list carries over.
Can you verify emails in a CSV file for free?
Yes, up to a point. Everything that can be decided without a mail server is free here and runs in your browser: syntax, duplicates (including Gmail addresses written with dots or +tags), typo domains such as gmial.com, and role addresses such as postmaster@. The tool also sends the list's unique domains, never the addresses, to a DNS lookup, which catches domains with no mail server and the RFC 7505 "null MX" that says a domain accepts no mail at all.
What a free file check can't tell you is whether each mailbox still exists. People leave jobs and close inboxes, and their addresses stay perfectly formed. That needs the SMTP conversation described in RFC 5321: ask the recipient's server about the address at RCPT TO, then disconnect. The first 10 addresses get that check here with no account, and the first 100 are free after a Google sign-in.
How do I remove invalid emails from a CSV?
Run the file through the checks in this order: syntax, duplicates, typo domains, dead domains, disposable addresses, then a mailbox check on what's left. The first five are fast and certain; the last one is the slow, metered step, so it should only ever see rows that passed the rest. That's the order this tool uses, and the "Download clean list" button gives you the file after the first five.
Keep the flagged rows rather than deleting them blind. A typo row often has an obvious fix (jane@gmial.com is almost certainly jane@gmail.com), and a row flagged as a business role address such as sales@ may be the owner's real inbox at a small company. If you prefer to script it, removing invalid emails from a CSV shows the same steps in Python.
Why does my verifier say a CSV has no email column?
Usually because the header isn't exactly email, the file uses semicolons, or the addresses are wrapped in Name <address> form. This checker scores every column by how many cells look like an address and picks the best one, with a header such as Email Address as the tie-break, so the header name doesn't matter. Semicolon and tab files are detected from the first line.
If the addresses are inside free text (a notes column, an exported thread), pull them out first with the email extractor, then come back with one address per row.
Is this faster than cleaning a CSV in Excel?
| This tool | Excel or Sheets by hand | |
|---|---|---|
| Find the email column | Automatic, by content | You pick it |
| Gmail dots and +tags as duplicates | Yes | Needs a helper column |
| Typo domains (gmial.com) | Flagged with the fix | Only if you know to look |
| Domains with no mail server | DNS lookup per domain | Not possible with formulas |
| Does the mailbox exist? | 10 live, then 100 free with sign-in | Not possible |
Excel's own route is a REGEXTEST formula (Microsoft 365) plus Remove Duplicates; see how to verify emails in Excel.
Who uses this tool, and for what?
- Cold emailers
- Check a scraped or bought lead file before it goes into your sending tool, so the first campaign from a new domain doesn't start with a bounce spike.
- Marketers
- Clean an old newsletter export before importing it into a new email platform, where a bad first send can get the account reviewed.
- Event teams
- Tidy an attendee or badge-scan CSV, where typo domains and duplicates from walk-up registrations are common.
- Agencies
- Run a client's list through the free checks before quoting for a full verification, so the quote is based on the rows that are actually left.
What can’t this tool tell you?
- The browser check covers the first 5,000 rows of a file; the free checks on your dashboard take the whole file.
- A clean result here means the rows look right and the domains take mail, not that each mailbox exists.
- Catch-all domains accept every address, so even a mailbox check can't confirm one person there.
- Microsoft and Apple consumer addresses (outlook.com, hotmail.com, icloud.com) aren't probed by our checker; they come back as risky, not valid.
Common questions
- How do I check if emails in a CSV file are valid?
- Drop the file into a CSV email verifier. It finds the email column, removes bad syntax, duplicates, typo domains and domains with no mail server, then asks each remaining address's mail server whether the mailbox exists. Here the first 10 are checked live with no account and the first 100 free after a Google sign-in.
- Is there a free email verifier for CSV files?
- Yes. This page checks syntax, duplicates, domains and disposable addresses for the whole file for free in your browser, runs a live mailbox check on the first 10, and gives 100 free email checks with a Google sign-in, no card.
- Does the tool keep my other columns?
- Yes. The clean download has every original column in the original order, with the flagged rows removed. The flagged rows download separately with a problem and detail column added.
- Is my CSV uploaded?
- No. The file is read in your browser. Only the unique domains are sent, to look up their mail servers. Addresses leave your device only if you run the mailbox check.
- What CSV format does an email verifier need?
- One row per contact with the address in its own column. Header names, delimiter and extra columns don't matter here. Addresses inside free text should be extracted first.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product 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
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
One plan, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.