What type of email is defined as an email that will send to unsubscribes, such as confirmations or sales receipts?

The correct answer is that this type of email consists of messages sent to unsubscribes, such as confirmations or sales receipts. These types of communications are usually categorized as transactional or operational emails. They are necessary for fulfilling requests made by the recipient and are not considered marketing communications.

Transactional emails include important information that customers expect to receive after a specific action they took—like making a purchase, confirming an account, or receiving a service. They are inherently different from promotional emails and can legally be sent regardless of a recipient's subscription status, as they are crucial for customer relations and support.

In contrast, the other options focus on audiences that specifically have subscribed or are internal, which do not include individuals who have opted out of marketing communications. Thus, they do not appropriately describe the nature of transactional emails.