Requesting a Read Receipt
It is possible to request a read-receipt to be sent to an address when the email is opened. To request a read receipt set the address with setReadReceiptTo().
To request a read receipt:
Set the address you want the receipt to be sent to with the setReadReceiptTo()
method on the Message.
When the email is opened, if the mail client supports it a notification will be sent to this address.
Note:
Read receipts won't work for the majority of recipients since many mail clients
auto-disable them. Those clients that will send a read receipt will make the user
aware that one has been requested.
$message->setReadReceiptTo('your@address.tld');
Parent topic: Creating Messages
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