Mail Receipt is a macOS application that adds delivery notification and read receipt requests to your e-mails.
Many e-mail servers will honour the Return-Receipt-To request and inform you that your e-mail has been placed into the mailbox of the recipient. This tells you that your e-mail reached the intended mail account but it does not tell you any more. Alone this automatic reply does not let you know if your e-mail has been read or seen.
In practice, a surprising number of recipients working for large organisations do honour the request for an automatic read reply. If the recipient's e-mail client supports read receipts, the e-mail software will likely ask the recipient if they wish to acknowledge your request for a read receipt.
There are clear issues of privacy, social expectations, and local culture that surround read receipts. Be aware that not every e-mail you send with these headers will be honoured and that some recipients might take offense. In other cases, recipients may appreciate the ability to automate the quick reply.