Read receipts are a way for people to acknowledge that they have received your email. The recipient can normally choose whether to acknowledge the receipt or not, so they are not a completely reliable way of checking if your emails have been received by someone.

You can request read receipts by enabling this option in the email composer's menu. To do so, go to OptionsRequest Read Receipt.

For read receipts that you receive you can define Evolution's behavior by going to EditPreferencesMail AccountsEditDefaultsMessage Receipts.