Text under "Tracking Options" indicates that response to requests for read receipts applies only to Internet accounts

When you are setting up a response to requests for read receipts under E-mail Options in Microsoft Outlook, the text in the Tracking Options dialog box informs you that the response that you specify applies only to Internet Mail accounts.

The tracking options may appear to work when you open messages from your Microsoft Exchange Server account. However, there are certain conditions that can cause unexpected behavior. For example, you may not receive a prompt to choose to send a receipt for certain automatically-processed messages.

Because the prompt to choose to send a receipt cannot be guaranteed in all cases for Exchange Server e-mail, Outlook states that the read receipt tracking options only apply to Internet Mail accounts. These accounts work consistently based on configured settings.