CloudMailin!

Mailgun is email automation for developers. Use our REST APIs to effortlessly send, receive and track email from your website or application.

Postmark removes the headaches of delivering and parsing transactional email for webapps with minimal setup time and zero maintenance. Send API and SMTP interface.

SMTP2GO is an email service provider, performing the task of reliably delivering transactional and marketing emails, and providing reporting tools to track and visualize what is happening with outgoing emails.