I'm sitting here cracking up laughing. I've seen clickbait articles, but this takes the cake. Dude can't even get the terminology right. An email client is Outlook, Thunderbird, web interface or anything used to access/view/send email. He meant to say ESP (email service provider).
As of this calendar year (2016), I've had zero (0) unsubscribes and spam complaints on my most profitable list. How? People are only allowed on that particular list if they maintain their monthly membership. I actually offer a benefit for list members that actually reduces their bottom line costs in their business every single month
. They are plumbers by the way. This isn't the regular MMO, diet, health and relationship crap most of the lemmings are trying to push every day.
I have friends that have turned absolute sh*t purchased lists into permanent monthly money makers without adding additional leads from less reputable sources. I'm willing to bet my first born, that if I mentioned a GRE, he'd be absolutely bewildered. Hell, his guru (chuckle) just started his website this past October that happens to be loaded with retargeting pixels.
There is no other medium available online anywhere close to the high ROI that email offers. None of the usual suspects like paid traffic, SEO or social come anywhere close. I'm also laughing at those numbers he used. Those numbers are for those whose notion of sending out emails is comparable to an fresh out of bootcamp infantryman on the front lines shooting haphazardly instead of an highly trained and decorated expert sniper marksman with dozens of kills to his credit eliminating high value targets.