Office 365 (Outlook Client) - How to Request a Delivery and/or Read Receipt
A delivery receipt confirms delivery of your email message to the recipient's mailbox, but not that the recipient has seen it or read it. A read receipt confirms that your message was opened. In Outlook, the message recipient can decline to send read receipts. There are other scenarios where read receipts are not sent, such as if the recipient's email program doesn’t support read receipts. There is no way to force a recipient to send a read receipt.
Tip: As a best practice, consider tracking only single messages of importance instead of all messages. Recipients who occasionally receive a notification that a read receipt is requested on your message are more likely to send a read receipt than if they are prompted every time that they receive a message from you.
Track a Single Message
1.In a new email message, on the Options menu, in the Tracking group, select the Request a Delivery Receipt check box or the Request a Read Receipt check box.
2.Compose your email and click Send.
Track Receipt Responses
1.Open the original message that you sent with a request for a delivery or read receipt. This message is usually located in the Sent Items folder.
2.On the Message tab, in the Show group, choose Tracking.
Note: Tracking doesn’t appear until at least one receipt has been received. After you receive the first receipt in your Inbox, it might take several minutes before the Tracking button is available.
For the most current information regarding read receipts and delivery notifications, please see the following Microsoft help article: https://support.office.com/en-us/article/Add-and-request-read-receipts-and-delivery-notifications-a34bf70a-4c2c-4461-b2a1-12e4a7a92141