The best way to confirm receipt of an email message on Yahoo is to request a confirmation from the recipient. If a failed delivery message is received, the user can assume the email was not received by the recipient.
As of December 2014, Yahoo does not offer an automatic read or return receipt message for emails sent through its client. To ensure delivery and receipt of the email, it is best to ask the recipient to acknowledge the email. This can be done by simply replying to the sender. Even if a failed delivery message is not received, there is no guarantee that the recipient opened or read the email.