I just spent a little time browsing similar questions on here, and it looks like some mail frameworks have a way of sending the proper signals to a mail client for the confirmation of read receipts.
The project on which I am working must have Read-Receipts requested as all the recipients have auto-sent read receipts enabled, and also have images blocked so I'm unable to use image-loading for tracking.
I'm most familiar with Python, Flask, and Flask-Mail, which is why I'm starting here to see if anyone knows a way to request this through these frameworks, or perhaps knows what to add to a to a mail header to request this.
Thanks!
So after a little more research and testing, in the absence of a specific setting in Flask-Mail for read-receipts, it is possible to request them by defining the header Disposition-Notification-To using extra_headers in the Flask-Mail Message() definition in order to trigger a read-receipt request:
sender = 'sender@domain.com'
recipient = 'recipient@anotherdomain.com'
msg = Message(subject='Testing Read Receipt',
recipients=[recipient],
sender = ('Testy McTesterson', sender),
extra_headers={'Disposition-Notification-To': sender})