Very Basic question about getting an email "subscribe" button for Wordpress [View all]

I'm maintaining someone's Worpress blog

(I believe it's wordpress.com as opposed to worpress.org, actually I'm not sure, it's the one we download and put on our own server)

I was surprised to find that there is not a simple setting to display a big subscribe button so that visitors will receive emails when a post is made. Or am I missing it?

Is there some plugin that will add a subscribe button? When I search for this, I usually end up with fancy plugins that will connect the blog to Facebook, Twitter, etc., but I already have that. In this case I just need an email sent to the subscriber, which is an option I can't find anywhere...

Maybe this is problematic because of spam issues, so a confirmation email would need to be sent to the user to confirm, but does such a plugin exist?