Looking for a good blog subscriber notification system

I need a solution that, ideally will:
- Send an excerpt of a blog post with a "read more" link back to the blog post.
- Send immediately when a blog post is published. This could be either a) automatically when published or b) triggered by the author.
- Allow nice formatting and layout of an email template.

We are currently using subscribe2 for some clients, but are finding it challenging to customise the email template. I also know of various solutions like mailchimp that send a daily digest or require manual creation of the email.

We also need a way for the subscribers to subscribe/unsubscribe in a nice way.