Active plugin to get followers

Greetings to You! ??

On the sidebar of my website https://www.ClaudioAdrianoDobre.com there is a widget-box named “Follow” where people who find interesting the topics that I write can insert their email to be automatically notified via email when I write a new article (I don’t have to do anything to notify them, they receive an email automatically from WordPress every time I write a new article). On the bottom-right corner of your screen, while on my website, there is also a “(+) Follow” button which does the same thing.

In time I noticed that these two functions are not very efficient because many people who take the time to write me to tell me they find my articles interesting, they do not join the list of followers by themselves before writing me, but if after thanking them for their interest I also explicitly tell them that if they want they can put their email in that box to be notified when I write something new, then they put their email joining the list of followers.

So I would like to implement a more efficient way to make people understand they can put their email to follow my website and be automatically notified when I write a new article. Essentially, I want to install another plugin that has the same purpose but that is more “active” because both the “Follow” box and the “(+) Follow” button are too passive.

I think a very efficient plugin would be a small window that pops up when the user is about to leave from the website by moving its mouse over the [x] button on the upper-right corner of the browser, which contains the same email field and a small text that I can write to invite the user to insert its email to become follower.
I have looked on the plugin database but I was unable to find anything like this, though I think there must be a free plugin that does this available around. Can You please point me to a free plugin that does what I described above? ??

I thank You for your kind attention and interest in helping ??