Evercontact's daily service for Office 365 analyzes your new incoming emails. It compares the signatures it finds in them to your address book to check if each contact is there and if they are up-to-date. When the service finds new contact update for you, you will receive a notification email which will remind you to go to your dashboard and save the contacts to your address book.
ContactRescue (formerly Flashback) is a one-time, paid service that scours your past emails. It extracts all the missing contacts and contact updates and then adds them to your address book.