How do I set up a RSS-to-email feature to easily convert your blog posts into email newsletter content and allow people to subscribe to these emails?

I think I already have a RSS feed set up, but I don’t recall how they’re aggregated. Do I have to create a WP_Query and select the type of posts I want and then check their RSS content, or do I need to dynamically create the RSS after I query the posts? And then how do I set up a way to allow users to register their emails and get a post every time there’s a new blog post?

The issue is how to generate the RSS content from the WP_Query (I guess I need to check the date it was created and only take posts that were generated in the last 24 hours and save the last post in a wp_option to make sure the same one doesn’t get delivered to all emails).

Then the other issue is how to send the emails. Do I create a cronjob that runs every day at midnight after creating a widget that allows people to put their email in a custom wp_table that the cronjob fetch from when delivering email through PHPmailer?