Will the the person know that he has been unsubscribed?

Typically, a person will not receive a notification when they are unsubscribed from a mailing list or service. However, if they try to access content or communications they previously received, they may notice the absence of those updates. Some services may send a confirmation email when unsubscribing, but this varies by provider. Ultimately, whether or not they realize they've been unsubscribed depends on their engagement with the content.