A whitelist is a list of people, companies, and mailing lists that are allowed to send email to you. It is a useful tool which is to make sure that in no case your friends' mails will ever be mistaken as spam. All emails from the whitelist will be regarded as legitimate.
Sources of whitelist are listed as follows:

• When Lockspam runs for the first time after installation, all the email addresses in your Address Book and Sent Items will be added to whitelist automatically. Meanwhile the emails in the Sent Items are taken as white mail models by Lockspam as it starts self learning.
• When you move a legitimate email from the Spam folder and send it to your Inbox, this particular email address will be added to whitelist.