There are many questions that your post does not explain...
What do you mean "article"?
Do you want to send them a link to a post?
Do you want to send them the contents of a post?
Do you want to send some text or html?
Do you want to send something AND have it available for viewing online?
I will caution you -- sending one email a day is going to upset MANY users.
If I get one email a day from a website, I unjoin that website ASAP