MailPoet – Email & Newsletter Marketing Plugins for WordPress
MailPoet started out as a free/premium plugin that turns your WordPress install into a mailing list service. Their new version continues this (free up to 2,000 subscribers), but also offers to deliver email for you.
This solves one of the challenging issues with running your own lists – ensuring messages don’t get caught in spam filters. For that matter, your host server could get blacklisted as well. So sending through your own server in the free version is best left to smaller lists that don’t send very often.
credit : MailPoet