You may have received e-mails from companies online that you have made a purchase from. At the very top of the e-mail in small print, the sender may ask you to insure that their e-mail address is included in your whitelist. A whitelist is a user-created database which lists email addresses, IP addresses and domains that they have determined are safe. Anyone added to the whitelist can successfully send email to the recipient (you) whilst the opposite is true – if you ain’t on the list you ain’t gettin’ in. For the database to be compiled you will need to manually add each of your trusted sources. Such a method is extremely thorough and whitelists offer close to 100% protection from spam.