Newletter helps in making loyal readers , Informing them about new contents , Informing them about deals and offers , Also making money via sending affiliate links in newsletter. WordPress has many newsletter plugins which are free to use. Although many offers pro version with some great features. Here is the list of some top newsletter plugin for wordpress.

Newsletter is a real newsletter system for your WordPress blog: perfect for list building, you can easily create, send and track e-mails, headache-free. It just works out of box!

News letter offers  Unlimited Subscribers with statistics , You can see who read the newsletter and when  ,Unlimited Emails with tracking which means you can track the ip details of users  ,Customizable subscription widget, page or custom form which helps you in getting a nice subscription form at front end.WordPress User Registration seamless integration this helps you to intall and use the plugin without hiring some one to set it up. Single And Double Opt-In plus privacy checkbox for EU laws compliance ,  Subscribers preferences to fine-target your campaigns ,SMTP-Ready, Customizable Themes , Html and Text versions of Emails,  All messages are fully translatable from Admin Panel (no .po/.mo) ,Diagnostics Panel to check your blog mailing capability, Compatible with Postman, WP Mail SMTP, Easy WP SMTP, Easy SMTP Mail, WP Mail Bank

Sendit is a friendly and easy newsletter and mailing lists plugin for WordPress, born to make newsletter delivery management a great experience. Sendit is not very popular newsletter plugin , yet is fulfill the demand of wordpress users. Sendit was popular in past .

Features

Add a subscription widget form in your sidebar or pages
Mailing list and subscribers management ajax powered in wp-admin
Double opt-in subscription widget
Custom post type integration
Send your posts to your readers with featured image
Build and send newsletter within WordPress
SMTP integration (works great with external SMTP services)

SendIt offer premium version with some more features.

MailChimp for WordPress – It is most popular newsletter plugin and service. Mailchimp offers you the best templates for newsletter , No spam facility , Most of emails directly land into inbox of the user , It also offers premium emailing service for bulk users. Sign-up forms which are good looking, user-friendly and mobile optimized. You have complete control over the form fields and can send anything you like to MailChimp.

MailChimp is free for lists up to 2000 subscribers, which is why it is the newsletter-service of choice for thousands of businesses. Mailchimp integrates with wordpress very easily. Default WordPress Comment Form  ,Default WordPress Registration Form , Contact Form 7 ,WooCommerce ,Ninja Forms , Easy Digital Downloads, Events Manager ,BuddyPress

Mailchimp is my personal recommendation to all.