Want to send automatic daily/weekly email to their subscribers.
Visitors will see a signup form on website (it would be simple form)
where they enter their email and name to subscribe the blog post.
An email will be send to their subscribed id to confirm the
subscription and after activation, subscriber will receive the updates
regularly until unsubscribe from the blog.
The process will be done from EMAIL SERVER.
You should know integration of email server and rss feed.
More detail can be provide for further communication.