Feature Requests for Subscribe by Email

The free wordpress plugin Post Notification has many robust features that should be incorporated into this paid plugin.
1. Allow subscribers to choose what categories to subscribe to
2. Nervous finger wait
3. Sender email address
4. Number of emails sent in a burst
5. Pause between transmission

The post notification plug-in is no longer being maintained.
Maybe you could look into maintaining it.
http://wordpress.org/plugins/post-notification/