IconVault's Email Normalizer turns a messy pasted email list into a clean, valid, deduplicated list in seconds. Paste addresses, flip on lowercase normalization and Gmail dot/plus normalization (so name.dots@gmail.com and namedots+spam@gmail.com count as the same person), then export the result as a clean text file. It is free and runs fully in your browser.

Every run shows live stats: total, unique, duplicates and invalid addresses, so you can see exactly what was removed before you send. Everything happens locally, which matters for mailing lists: your addresses never leave your computer and are never uploaded to a server.