Email List Health Report

✓ Email verification

Paste a list of addresses and get an instant quality report — duplicates, syntax errors, role and free-provider addresses, likely typos and domain concentration, all analysed in your browser.

No sign-up required Runs on our own infrastructure Also available via API
Everything is analysed in your browser — nothing is uploaded.

Before you upload a list to a verifier — or worse, straight into a campaign — it’s worth a thirty-second look at what you’re actually holding. Most lists carry the same handful of problems: the same address pasted twice, a few gmial.com typos, a pile of info@ and support@ role mailboxes, and one domain that somehow makes up half the file. None of that needs a server to spot. This tool reads your list entirely in the browser and hands back a structural health report you can act on immediately — nothing is uploaded, nothing is stored.

What it checks — and how

Everything here is a structural check: it reasons about the text of each address, not about whether the mailbox is real. That’s exactly the set of problems you can answer instantly and privately:

  • Duplicates. Exact repeats after normalising case. Deduping before you verify saves you paying to check the same address twice.
  • Syntax. A practical, RFC-ish pattern — a local part, one @, and a domain with a real TLD. It catches the obvious breakage (missing @, trailing commas, a bare domain) without pretending to be the full grammar.
  • Role-based addresses. Shared mailboxes like info@, sales@ and abuse@ that usually aren’t a single consenting person — see the verifier for why senders treat them differently.
  • Free providers. Gmail, Yahoo, Outlook and friends. Not a problem in itself, but a B2B list that’s mostly free mailboxes is telling you something about its source.
  • Likely typos. Domains one or two edits away from a big provider — gmial.com, yahooo.com, hotmial.com — with a “did you mean” suggestion.
  • Gibberish local parts. A conservative heuristic that flags long, vowel-starved, random-looking local parts that are often bot signups.
  • Domain concentration. The top five domains by share, so a single-source import or a leaked signup form stands out.

How the quality score is built

The score is deliberately simple and transparent so you can trust it: it’s the share of addresses that are clean — meaning unique, syntactically valid, not role-based, not a likely typo and not gibberish — out of everything analysed, expressed out of 100. A list of 100 addresses with 10 duplicates, 5 role mailboxes and 5 typos scores around 80. It’s a rough triage number, not a deliverability guarantee: two lists with the same score can behave very differently once you actually try to deliver to them.

What a local check can’t tell you

This is the honest part. Reading text can’t confirm that a mailbox exists, and it can’t see three of the things that most affect deliverability:

  • Whether the mailbox is real. A perfectly-formed address can still bounce because nobody’s home. Only an SMTP-level check knows.
  • Disposable domains. Throwaway providers spin up new domains constantly, so a static list can’t keep up — that’s a job for the disposable email checker.
  • Catch-all domains. Some servers accept mail for every local part, so “it accepts” doesn’t mean “it’s real.” The catch-all checker flags those.

Treat this report as the fast first pass: clean up the structural problems here, then run the survivors through real verification. The email list health cheat sheet walks through the whole sequence.

Privacy

The analysis runs in JavaScript on your machine. Your list never leaves the page — there’s no upload, no request, and nothing kept after you close the tab. That makes it safe to paste customer data you wouldn’t want to send to a third-party server just to count duplicates.

Frequently asked questions

Does my list get uploaded anywhere?
No. Everything runs in your browser — the list is never uploaded, never stored, and is gone when you close the tab. Safe for sensitive data.
Can this tell me if an email address is real?
No — reading text can’t confirm a mailbox exists, or spot disposable and catch-all domains. That needs live checks. Use the email verifier for real verification.
How is the quality score calculated?
It’s the share of addresses that are clean — unique, valid, non-role, non-typo, non-gibberish — out of everything analysed, scaled to 100. A triage number, not a delivery guarantee.
Is there a limit on list size?
It analyses up to 1,000 addresses per paste and tells you when it truncates. Paste in batches, or verify a whole file at once with bulk verification.