To use this feature, you need an Office 365 work or school account, or an Exchange on-premises account. Supported applications include Outlook for Office 365 and Outlook 2019 for Mac version 15.35 (170610) and later (select Outlook > About Outlook to check your version).

Read receipts and delivery notifications are available in only some versions of Outlook for Mac, and only when using an Office 365 work or school account, or an Exchange Server account managed by your organization. This option will send a request for a read receipt with a single message that is sent from your Outlook client.

Request Receipts when Sending Single Message.

You can verify that an email you sent is delivered or read by requesting a delivery or read receipt in the Microsoft Outlook 2019 or 2016 email client.

Read receipts and delivery notifications are available in only some versions of Outlook for Mac, and only when using an Office 365 work. Read receipts are not supported in Outlook for Mac.

Outlook for Mac doesn't include the ability to turn on or turn off read receipts.

Microsoft outlook read receipt