How to check contact read email or not when send email to Individual?
You might need to try installing the Transactional Emails extension which aims to address the limitation of CiviCRM which only handles the tracking of emails sent through civimail.

This extension tracks bounce, click, open events for single emails sent from civicrm, either with Send Email action, scheduled reminders, contribution receipts, etc.

The description on the extension link explains in detail on how to install and check the report of these events.