Currently, the only way for HubSpot to be able to track Emails is by adding tags (pixel, or alike) to the emails, so when the email is opened or some link clicked, HubSpot gets informed.
These tags are added by HubSpot while using HubSpot plug-ins or using HubSpot applications.
We do not use HubSpot at all to send emails, but a third party, MailChimp, to deliver our emails.
It would be great if there was an API so HubSpot would provide a set of tracking tags generators, so we could add these to our backend generetated emails.
Thank you,
Ezequiel.