An excerpt from http://www.sitepoint.com/wordpress-email-marketing-plugins-vs-all-in-one-options/ , by Jacob McMillen
Signing up to an email marketing service provider is a big commitment in terms of cash; too big for many.
The beauty of running a WordPress blog is that there are free and low-cost plugins for everything. There are dozens of email marketing plugins that can instantly get your site ready to go.
Unlike a one-size-fits-all solution, plugins are used to fill specific needs wherever you find them. They give you the flexibility to customize your site to your near-exact specifications. While this can be extremely cost efficient, a bundle of plugins can sabotage your site’s load speed, which is a MAJOR marketing no-no.
Premium plug-ins can be better but you can still run into server and deliverability issues.