Clean & Validate Your Email Mailing List CSV

A dirty mailing list costs you money. Invalid email addresses increase bounce rates, hurt sender reputation, and can get your account suspended by your email service provider. Duplicate entries mean you are paying to store and email the same person twice. Formatting inconsistencies cause import errors.

This CSV editor lets you upload your mailing list, validate email addresses with a single click, remove duplicate rows, and export a clean CSV ready to import into Mailchimp, Constant Contact, Sendinblue, or any other ESP. Everything runs in your browser — your subscriber data never leaves your device.

Email service providers like Mailchimp, Constant Contact, and Sendinblue charge based on subscriber count. Every invalid or duplicate email on your list is money wasted. Worse, high bounce rates from invalid addresses damage your sender reputation, which means more of your emails land in spam — even for valid subscribers.

Most businesses accumulate list hygiene problems over time. Contacts from trade shows are entered with typos. Old employee addresses linger after people leave companies. Customers sign up with disposable email addresses. A quarterly cleanup using this tool keeps your list healthy and your deliverability high.

For businesses migrating between ESPs, cleaning the list before import prevents importing known bad data into a new platform — giving you a fresh start with clean data.