The Address Book feature allows registrars to add frequently used email addresses and have them present as a dropdown in the cc and bcc fields when sending emails. 

Go to Email Settings > Address Book > Add. You can add commonly used email addresses to the address book through this page. The selected emails will be presented as a dropdown option under custom and marketing emails. This will relieve registrars of the manual work of remembering and typing in the email address as each email is sent.