EmailOctopus is a lightweight email marketing tool that runs on Amazon SES infrastructure. The free plan doesn't offer as many features as the other free email marketing tools on this list, but you can send far more emails per month than most. You can send unlimited emails from any number of email addresses. This makes it the perfect solution for small agencies and entrepreneurs representing other brands. It also integrates with third-party apps like MailOptin, WordPress, and Zapier, so you can share customer data across different tools.