How to mark a sender as safe?

If you add them to your Contacts, they should be ignored by the Junk mail filter.

Select the mail address and click on drop down arrow and add to vip , it will marked with star icon and will indicate that this contact is a vip and safe in every sense , but it doesn't mean its safe the sender can send a spam mail to you in future ( as it's all good faith ) , but the contact can be added in address book .

Also address book is meant for saving contact details and not for filtering junk mail .