Mailgun - Transactional Email Service
Mailgun's service allows you to easily deliver email messages to your users which may be generated by actions on your website. With the Free Tier plan, you can send up to 10,000 emails per month which is alot if you're now starting up. This plan gives enough opportunity for a startup to gain enough traction and revenue before having to pay for using this service for sending over 10k emails per month. This is an ideal service to use while keeping it lean. In fact, we currently use Mailgun to send out emails that are generated from within ShoutBlast's website.