OSD Subscribe

OSD Subscribe is a simple and highly flexible email subscription plugin. OSD Subscribe allows you to modify the content
before and after the subscription form, create pages for subscription confirmation and unsubscription, modify error
and success messages, completely customize the email templates, and have different subscription forms for
different categories on different parts of your site. OSD Subscribe can be used as a widget or as a shortcode,
so there is no place this plugin can’t go. In addition, OSD Subscribe provides a filter for users to completely customize
the layout of the form.

A Brief Feature List

1. Email template customization
2. Full error and success message customization
3. Full form customization via filters
4. Provides a shortcode and a widget
5. Different subscription forms for different categories on the same site (or even same page!)
6. Manage subscribers
7. Can handle large amount of subscribers
8. Uses AJAX for email subscriptions
9. Easy to style
10. Minimal code
11. Fast processing
12. Unlimited subscribers (as many as your database can hold)
13. Subscriber exporting and importing to/from CSV

Link to plugin page WordPress plugin page.