The corresponding table stores the e-mail address and the IP from which the email was received. One mouse click in the SPAM checker form adds any received e-mail to this list.
As soon as you added a sender to the 'white list', any e-mail from this sender or from this IP will be accepted and displayed on green background. Nervertheless, you may delete an e-mail from this sender but you cannot assign it to 'SPAM' as long as the record is in the list. If you should receive SPAM from an IP belonging to a member of the 'white list' set the flag ignore IP.