How to "attach" a link to a letter?

Question

PHP

Greetings.
The task is quite simple. Let's say I make a newsletter and send someone an email with a link. If the recipient clicks on this link, he will receive some kind of bonus. For example, he will receive a discount on a product.
But what if this recipient sends this email to someone else. Or just send this link to someone else. Then this outsider will be able, by clicking on the link, to also receive a discount.
So here's the question. Is there any way to determine if a link was clicked from a particular mailbox?
Or is there another way to solve this problem?
Thank you.

Answer 1

there is no such way