What I need is a mailing with mail tracking system.

When ever we post a article in the blog, we should be able to send those to the people who are subcribed for those categories (the category of the posted article) from the wordpress admin area. This feature is mostly expected by all the developers and the webmasters as well.

Also another important feature with this system is that, the administrator can check how many users have viewed the email that was send each time.