The app supports requesting a “read receipt” when composing messages. Go to the top right and tap the three dots. In that menu tap on "Request read receipt".

You are also able to automatically send the request on a per-account basis. The option is located in Settings > Manage accounts > Your e-mail > Options > Composing and sending.

Note that not all apps support read receipts on the receiving side. Gmail, iPhone Mail or built-in Android Email (the stock version from Google) do not support this feature.