Atomic TLD Filter Version 1 descriptions Atomic Top Level Domain Filter is a software program that allows users to automatically select certain e-mail addresses from the list based on the professional or national basis. When is it necessary & who needs it? Just a simple example - in order to get maximum return from your marketing campaign you need to split your mailing list into specific target groups & optimize your message for each one. This is when ATLDF comes in handy separating emails into these groups - for example . edu zone for marketing to students & academia . es for reaching the Spanish only . com for contacting companies.