phpmailer - How to get acknowledgement email once after user read it using PHP? -

how acknowledgement email once after user read using php?

please find process

1) send email recipient.
2) recipient read email.
3) if recipient read email, acknowledgement send sender.
4) need achieved using php.

please suggest me on this.

you tagged phpmailer i'm guessing you're using phpmailer class.

there have to

$mail = new phpmailer();  $mail->ismail();  $mail->from = $senderemail $mail->confirmreadingto = $confirmemail ... body etc here ...

if not using phpmailer have add "x-confirm-reading-to" header email.

And