Robin Rendle, who writes the email newsletter for CSS-Tricks and has a email newsletter of his own called Adventures in Typography, quotes a bit from Robin Sloan’s book How to Make a Book:

Of all the followings you can accrue—on Facebook, Instagram, Twitter, and platforms yet to be invented—one is more important than the rest by an order of magnitude. It’s the group of people who have given you their old-fashioned email addresses and agreed that they would, from time to time, like to hear from you. Even if no one quite loves their inbox, everyone has one. Across generations and geography, through digital fads and fascinations, email is the common denominator, the magic key.

Email lists grow slowly, but their growth is sturdier than social networks. It’s exciting to see the sharp little bursts of attention on the social networks when something you write takes off. But it’s easy come, easy go; as quickly as attention finds you, it moves on, eager for the next thing. Email lists are sturdier and stickier. There is a real sense, you’ll find, of building them one person at a time.

Robin (Rendle) goes on to say about email:

After an email goes out there’s often nothing but radio silence from the other side and then I begin to worry for half a second whether anybody is reading them at all. I probably just have to remember that every social network has been training me as a writer, for the better part of a decade now, to be dependent on those likes and faves and retweets for my emotional well-being.

It’s pretty much radio silence. Once in a while, people respond to the newsletter with something they’d like to share or some little anecdote. I should do a better job at passing those along to the team, but Robin’s point stands, it’s nothing like the engagement feedback you get on other platforms, which is weirdly at odds with the fact that the actual engagement is likely much higher.