Send Email to Members Only for New Posts and/or comments

I have a membership site built on WP, Wishlist Member, OptimizePress.

I would like my site to send an email to my subscribed members that notifies them when I post, and to include the post content itself within the email.

If possible, an option to send it out as one email per day (Digest Mode) or one per post (Regular Mode).

Does this exist anywhere in WP world?

Thanks.