MailPoet is great by allowing to use any WordPress or WooCommerce ressource in your website, but the MAJOR drawback of having a WordPress integrated newsletter solution like MailPoet is hotlinking!
As you need customers to view your emails images, and as MailPoet do not embed them in the email (which is great!), you live a hard time fighting hotlinking as every directory must accessible to any webmail domain your customers may use!
But if MailPoet could copy any image used in an email under a specific directory (even better if in subdir of this directory) prior to sending it, webmasters would just have to allow free access to this directory.
Everything else could be protected against hotlinking!
In the way I see it for now, MailPoet is a real SEO killer to websites as a consequence of that hotlinking issue that allows toxic backlinks you then need to disavow in Google Search Console...
I really wish you could add a new feature to do so (copy files in a different directory).
As a second gain, your emails woule remain visible and accurate as long as you keep the email specific directory. Even if you delete the original image (or product for that matter if you use WooCommerce)!
I hope you'll be interested in such a feature.