In the default email app, Menu/Settings/Account settings/Sending mail/Read receipt. Check the box. Don't expect a receipt for every email that was read. Some email clients ask whether the receipt should be sent, and the recipient can say no. Others can be set to ignore receipt requests. And some still send a receipt when the email is received, whether it's opened or not. So even if your address is filtered to delete your emails on receipt, you'll still receive a read receipt. It's an old try to make email seem more like snail mail, but it's iffy at best.
