We would like to figure out how to see if messages sent from chatter have been opened like in the email marketing app.

For example, when we send a customer an invoice, we can see if the email was sent successfully by the color of the envelope icon (grey it sent, red it did not).  We are not sure if we are having problems with emails from Odoo being marked as Spam by some and it would be nice to see if an email was in fact opened by the recipient from within the Chatter section.

We are using the Odoo online and have Studio to make any modifications.