Microsoft Outlook will send a read receipt when a new message requests for read receipt. Sending read receipt option is by default enabled in Outlook. And if you do not want to send a read receipt request then you can disable using the options available as part of Outlook settings. Listed below are the steps to disable sending read receipt in Outlook 2016, 2013 and Outlook 2010
Step 1: Click File menu and select Options from the menu list.
Step 2: In the Options window, click to Mail tab and screen down to Tracking section.
Step 3: Select the radio option “Never send a read receipt” under “For any message received that includes a read receipt request”
Step 4: Click OK to confirm and save the changes.
Demo Video – Disable sending read receipt in Outlook 2010
Also See: Request for delivery message and receipt message in Outlook