Our email application contains an automated unsubscribe list, or "Suppression List". When you send a campaign through our system we include an unsubscribe link at the bottom of any emails that we sent. When a recipient opts out of your campaign they are automatically added to your suppression list to ensure that they do not receive any further emails from you.
Additionally, the suppression list also records hard bounces (invalid email addresses) so that you do not send emails to addresses that are no longer valid. This process is also handled automatically to save you time.