1. Your list
A CSV exported from a spreadsheet, CRM, shop or another email platform.
Optional: a do-not-email list (unsubscribes, bounces, complaints)
Paste or choose addresses you must not email again: one per line, or any export that contains them. A line like @example.com blocks a whole domain. Matching rows move to the rejected file so the import cannot re-subscribe them. Read here in your browser, like the list.
Choose a file or paste the text, then click Check list.
Result
Heading names by platform
| Platform | Expects for email | Your file | Other headings that would match if renamed |
|---|
Safe fixes
What it checks, and what it leaves out
- Email syntax: missing or doubled @, spaces, "Name <address>" form, several addresses in one cell, bad characters, a domain with no dot or an impossible ending. Blank emails and stray whitespace are listed too.
- Duplicates: the same address ignoring capitals is a duplicate. Gmail ignores dots and "+" tags, and a few other providers ignore "+" tags, so those are flagged as likely duplicates for you to review, never removed for you.
- Typos: common misspellings of gmail, hotmail, yahoo, outlook, icloud and similar, and endings like .con, .coom and .cmo, each with a suggested fix.
- Role and disposable addresses: info@, admin@, support@, sales@, noreply@ and similar; and a small built-in list of throwaway-inbox domains (it is short and will miss many).
- Placeholders and wrapped addresses: test@test.com, none@none.com and similar fillers are flagged;
mailto:,Name <a@b.com>, quotes and trailing punctuation are stripped by the safe-fixes copy instead of rejecting the row, and internationalised domains are written in punycode. - Excel damage: a byte order mark, scientific notation, phone and ZIP columns that lost digits,
.0endings,#NAME?values, mojibake, semicolon or mixed separators, and rows with the wrong number of cells. - Consent hints: it looks for a subscription, opt-in or unsubscribed column and counts rows marked unsubscribed or bounced, so they are not re-imported as subscribed.
- Safe fixes trim spaces, lowercase emails, drop the BOM, use commas, optionally rename headings to the platform's names, keep the first of exact duplicates, and (only if you opt in) fix typo domains. Rows with a blank or invalid email, the wrong cell count, or an exact duplicate go to the rejected file with the reason; nothing is silently dropped. Names, phones and other values are never rewritten.
- Not checked: whether an address exists or will bounce (no mail server is contacted), whether anyone agreed to be emailed, whether a role or disposable address is acceptable for you, and anything a platform changes in its importer.
Common questions
Why does my Mailchimp or HubSpot contact import fail or skip rows?
The usual causes are an email column the importer does not recognise (a heading that is not exactly what the platform expects), addresses with a space, a comma or a missing dot in the domain, blank email cells, a semicolon-separated file saved by Excel, and rows with the wrong number of cells that shift every column after them. Paste the file here to see each one with its line number.
How do I check an email list for typos like gmial.com before importing?
The checker compares every domain with a list of common provider typos (gmial.com, gmal.com, hotmial.com, yahooo.com, outlok.com, .con and .coom endings) and shows the likely fix next to each address. It is a guess, so the cleaned file only applies the fixes if you tick the box, and every change is listed.
Does this verify that an email address exists or will not bounce?
No. It checks spelling and structure only. It does not contact any mail server, so it cannot tell whether a mailbox exists, whether a domain accepts mail, or whether an address will bounce. Use your email platform's own validation or a verification service for that.
Does it tell me whether I am allowed to email these people?
No. Nothing in a CSV proves anyone agreed to be emailed. CAN-SPAM, GDPR, CASL and similar rules, and each platform's terms, are your responsibility. The tool only points out a consent or unsubscribed column if there is one, and warns when rows are marked unsubscribed or bounced so that you do not re-import them as subscribed by accident.
What are role accounts and why flag them?
Addresses like info@, admin@, support@, sales@ and noreply@ usually reach a shared inbox or nobody. They tend to produce more complaints and fewer opens, and some platforms suppress or reject them. They are flagged, not removed: whether to keep one is your decision.
Why did Excel change my phone numbers and ZIP codes?
Excel stores long digit strings as numbers: 5555550101 can become 5.56E+09 with the lost digits gone for good, and 02108 becomes 2108. This tool flags both, but it cannot restore digits Excel threw away, so it never rewrites those cells. Re-export from the source with the column formatted as text.
Is it safe to put my customer list into a web page?
The page runs in your browser, the file is read locally and nothing is uploaded; a test in the code asserts there are no network calls. Your own privacy policy and data-handling rules still decide what you may open on a given computer.