This leads to the idea of opt-in. If they choose to receive such emails, they must express this choice by undertaking some action. This means that each email address has been submitted together with a request to be added to the list of addresses used when sending out the newsletter or marketing messages in question. Responsible publishers and marketers only use opt-in subscriber and address lists. They suggest that people may sign-up to a list inadvertently and should be given the chance to confirm their decision before actually being added to a list.
Some people submit other people's email addresses.
The actual owner of the address may not be aware of this action, nor agree with it. We'll look at this next week.