Mixpanel for example, provides a mechanism [1]. [1] https://help.mixpanel.com/hc/en-us/articles/115004690106-How-can-I-track-email-open-rates- https://help.mix

Mixpanel for example, provides a mechanism [1]. [1] https://help.mixpanel.com/hc/en-us/articles/115004690106-How-can-I-track-email-open-rates- https://help.mixpanel.com/hc/en-us/articles/115004690106-How...