When you compose your message, click the Options icon in the top toolbar.
The expanded message icons are shown.
From the Receipt: drop-down menu, select the type of return receipt that you want to request.
The drop-down menu displays the following options:
None: No receipt is returned.
Read: Receipt is returned when the message is read.
Delivery: Receipt is returned when the message is delivered.
Read and Delivery: Receipt is returned when the message is both read and delivered.
When your recipients receive your message, they are asked to verify that they have received it.