Ignoring the terminology errors, and the fact that this is a pretty scummy and uninteresting business model (it's kind of like blogging about the awesome architecture you built to predict when people will be at home eating dinner so you can robocall them with telemarketing crap right then), this kind of system is also inherently unreliable.<p>None of my email clients, on OS X, Windows, or Linux, will show that pixel unless I press a button or take some action.<p>And I believe that is increasingly the default behavior of email clients, isn't it? Which means this technique will increasingly not work, and there is nothing close.io can do about it.