Click [Setting] to display [Setting] screen.
Click [Read Receipts] link in the left side of the window.

To use read receipt

Request read receipt for all messages I send

Choose whether you want to request read receipt always.
Choose one of them.

No

The read receipt is not requested as default.

Yes

The read receipt is requested as default.

Respond to requests for read receipts

Specify how it responds to requests for read receipts.
Choose one of them.

Never send a response

No read receipt confirmation screen displayed.

Ask me before sending response

The confirmation screen is displayed when you open messages that requested response.

Send a response automatically

No read receipt confirmation screen displayed, but the response is sent automatically.