Read Receipts can easily be disabled on a per message basis at the Outlook client by clicking the No button.
If you wanted to go the extra mile you can setup a rule within Exchange that would disable them on all inbound emails.
Create a new mail rule and select modify message
In the new rule window give it a name “Disable Read Receipt”
Apply this rule to all messages
Do the following and select “Remove this header” and enter the text “Disposition-Notification-To”
Now the header details that are requesting the read receipt are removed from the message and no action will be required from the end user.
If you wanted to perform the same task from the Exchange Management Shell you can run the following command:
New-TransportRule -RemoveHeader 'Disposition-Notification-To' -Name 'Disable Read Receipt' -StopRuleProcessing:$false -Mode 'Enforce' -Comments '
' -RuleErrorAction 'Ignore' -SenderAddressLocation 'Header'