Apple Mail - Read Receipt

No. Only certain email service providers offer that feature. It is not something that the Mail app incorporates.

Basically it's nobody's business when or even if someone reads or opens a Mail message.

You're welcome. I had been looking for this earlier Discussion and just came across it:

John Galt wrote:

Email is not the exclusive property of Apple or PCs to manage.

Even "in the PC world" such delivery status notifications are considered unreliable for a wide variety of technologically sound reasons. The SMTP standard addresses how to implement them, but as it repeatedly emphasizes they are strictly advisory in nature.

Due to the nature of SMTP delivery status notifications cannot be encrypted and are therefore subject to forgery, intentional or inadvertent tampering, and are utterly inappropriate for the legal purposes you describe. No responsible legal authority relies upon them. A knowledgeable defense attorney (as though your deadbeat clients could afford one) would instantly demolish any attempt to introduce them as evidence in a legal proceeding.

If that weren't bad enough the privacy concerns I alluded to have prevented such practices from becoming accepted.

How do I get a return receipt showing when someone opens an email? - Apple Community

I do want to know sometimes whether my email has been received/read.

I run this code in Automator before I press send.

Send the email.

Then in the pop-up window select 'continue' which then resets the return receipt back to normal eg not requesting subsequent recipients for a receipt.

This works on occasions but I understand that doesn’t always depending on the set up of the receiver.

Note substitute, obviously, your relevant email address in full instead of <your email address>