Clean an email list

Why lists need cleaning before they are used

An email list collected over time is never tidy. It has capital letters where there should not be, spaces copied in from a spreadsheet, addresses typed with a comma instead of a dot, the same person three times, rows that are not emails at all, and entries pasted in with names and angle brackets around them. Sending to a list like that means bounces, and bounces hurt your sender reputation, which means fewer of your genuine emails reaching the inbox. Cleaning takes seconds and is worth doing every time.

What the cleaner does

1. Extracts every email address it can find in the text you paste or the file you drop, so messy input such as "Ada Lovelace <ada@example.com>" or a whole CSV row still yields the address.
2. Normalises each address: trims spaces and converts to lower case, because mail servers treat Ada@Example.com and ada@example.com as the same mailbox.
3. Validates the structure: one @, a domain with a dot, no spaces or illegal characters. Entries that fail are removed and counted.
4. Deduplicates, keeping the first occurrence in the original order.

The result reports how many addresses came in, how many were invalid and how many duplicates were removed, so you can see what the cleanup did.

What validation can and cannot tell you

Structural validation catches typos and junk: missing @, "gmail,com", trailing punctuation, an address with a space in it. It cannot tell you whether the mailbox actually exists or whether the person still wants your email. That needs a verification service that talks to the mail server, and for that you are sending your list to a third party, which is a decision to make deliberately. This tool is the safe first pass, done entirely on your device.

Output format

One address per line is the format every mailing tool's import box accepts by paste. CSV output adds a header row and is what you want for uploading as a file to a mailing platform or a CRM.

Typical uses

• Preparing an event sign-up sheet for a newsletter import.
• Merging exports from two systems and removing the overlap.
• Cleaning a list before a bulk send so that bounces stay low.
• Pulling every address out of a long email thread or a document.

Email lists are personal data. This tool never uploads them; the cleaning runs in your browser and the list exists only there.