Atomic Top Level Domain Filter (ATLDF) 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 and 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 and 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 and academia, .es for reaching the Spanish only, .com for contacting companies.