Without trying to hijack your thread, I'm curious exactly HOW opens are tracked by these apps. They seem to stand by them (but they're evil marketing people).

Seems liek they just embed an image in your email. When it loads, they have a unique ID so they know which email was opened. Now, most email apps are starting to block images from displaying by default. Wouldn't this HUGELY skew the open rates? And if these rates are inconsistent (image week 0 default gmail is to open images, week 3 it's turned off... how could you make that comparison?)

So you could have massive swings in open rates due to a specific provider changing their policies. Or any number of other reasons.

So why do you track opens at all? Isn't that metric so inconsistent and inaccurate that it'd be better to track something else entirely?