Is there a reliable way to certify (ensure, track) the delivery of an email message when using smtplib?

For example:
Disposition-Notification-To message header which enables the e-mail reader of the recipient to send confirmation e-mail when the recipient opens the message for the first time. That e-mail reader program must support this functionality.

Return-Receipt-To message header which enables the e-mail server of the recipient to send confirmation e-mail when the original e-mail gets received by that server. However, most newer e-mail servers do not support Return-Receipt-To header.

Are these message headers at all reliable?

The request is to enhance the documentation to provide an example of how to track a message delivery. Conversely, if it's plain not possible, the request is to state that explicitly in the docs.

This looks more like a question than an issue.  Have you tried stackoverflow or a user forum?

Yes, it's a question which could lend itself well to a documentation issue.

I've looked at things like:
https://stackoverflow.com/questions/54047021/python-smtplib-how-to-use-disposition-notification-to
https://stackoverflow.com/questions/40369645/detect-bounced-emails-in-python-smtplib

But I'm not seeing a generic approach which would let me prove messages got to the destination. It seems Disposition-Notification-To is not always available.