Appended data is a data process whereby a customer file has additional data appended to it; like age, income, home value from some external data file. Usually used in the context of Email appending or e-appending. Appended data is used as a marketing practice to take known customer data, like first name, last name and postal address and then matching it against a merchants’s database in order to get email addresses. The main objective of appending data to existing files is to increase one’s email subscriber list so they can send customers information via email. Appended data is somewhat controversial, with some critics stating that this type of email sending to people who never actually opted-in is a bad practice. On the other hand, some experts state that if done properly, appended data is a really good way for marketers to provide offers to their already existing customers.