In what situation is a read receipt notification not sent when an email is opened or previewed bya recipient? O when the recipient selects to disallow the sending of the receipt
O when the recipient has previewed but has not opened a message
O when the recipient reads and then permanently deletes the message
when the recipient uses the Reading pane to open the message

when the recipient selects to disallow the sending of the receipt

Explanation:

A read receipt notification allows the sender to know when the receiver has opened the message he sent. However, there are cases when the read receipt may not be delivered. The recipient has the option not to allow the sending of the receipt. In this case, some people want privacy so they don't want the sender knowing when they opened the message. In other case, the email program of the recipient simply doesn't support it. Therefore, the read receipts will not be sent.

that would be my answer.

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