Doesn't 55% seem too low? I probably open 95% of my emails on my phone first, because of the instant notification. Usually just a quick glance before I open up my desktop email client. How are they even tracking this? Does it take into consideration repeat views like in my case? Also, what about the email subject & snippet that is shown in a notification?
It's gotten to the point where email is basically worthless anyway. You can't load images, because they are trying to track you. You can't ever click on a link safely, because you are trying to track you. It's become little more than a (poor) notification system directing you to go (manually) log into a website or something. Very frustrating and disappointing to see what has become of the medium.