Clean the list before
it cleans you out

No — and for this tool that's the whole point. A lead list is commercially sensitive data, and 'free list cleaning' sites that upload it are paying themselves with your data. Here the CSV is parsed and cleaned entirely in your browser's memory; close the tab and it's gone.

Four categories: addresses with broken syntax (guaranteed hard bounces), exact duplicates (after lowercasing), disposable inboxes (mailinator and friends — dead by the time you send), and optionally role accounts (info@, sales@…) which reply rarely and report spam often. Each removal is counted so you see exactly what happened.

It samples the first rows and picks the column with the most syntactically valid addresses — so it works whether your export calls it 'email', 'Email Address' or 'correo'. All other columns pass through untouched, and the original order is preserved.

Honestly, no. Structural cleaning removes the guaranteed bounces, but a perfectly-formed address whose mailbox was deleted last month looks identical from the outside. Catching those needs SMTP-level verification per address — run your cleaned list through a verification service (Norbelys verifies on import) before a big send.

Under 2%. Gmail and Microsoft read bounce rate as list-quality evidence: past roughly 2–3% hard bounces, your whole domain's reputation pays for it. Structural cleaning plus real verification gets well-sourced lists under 1%.