Read Receipts in Outlook Web App
A read receipt confirms if your email was opened by the recipient.
To request a read receipt for an outgoing message in OWA, click the extended menu while composing a message and click show message options.
Once the message options box appears, check Request a read receipt and click OK.
User's who receive messages with read receipts in OWA may see the following message upon opening:
When the user has opened a message with read receipt enabled you will receive an email notifying you.
In iOS Mail, and e-mail for Android, read receipt responses are sent by default. Please note that some mail clients may allow user's to neglect sending read receipt responses.