May 14.2018 - Version:
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.
Screenshots Mail Receipt for Mac