Read-receipts
Some email applications, such as Microsoft Office Outlook, employ a read-receipt tracking mechanism. The sender selects the receipt request option prior to sending the message, and then upon sending, each recipient has the option of notifying the sender that the message was received and/or read by the recipient.
However, requesting a receipt does not guarantee that you will get one, for several reasons. Not all email applications or services support read receipts, and users can generally disable the functionality if they so wish. Those that do support it aren't necessarily compatible with or capable of recognizing requests from a different email service or application. Generally read receipts are only useful within an organization where all employees/members are using the same email service and application.
Depending on the recipient's mail client and settings, they may be forced to click a notification button before they can move on with their work. Even though it is an opt-in process, a recipient may consider it inconvenient, discourteous, or invasive.
Read receipts are sent back to your Inbox as email messages. Additional technical information, such as who it is from, the email software they use, and the IP addresses of the sender and their email server is available inside the Internet headers of the read receipt.
The technical term for these is MDN - Message Disposition Notifications, and they are requested by inserting one or more of the following lines into the email headers: X-Confirm-Reading-To: Disposition-Notification-To: or Return-Receipt-To:
Read more about this topic: Email Confirmation