Transactional Email Templates by Postmark - Open source email templates for use in your SaaS app.
Amazon SES - Scale your business email & marketing messages with Amazon Simple Email Service (SES), a cost-effective and reliable cloud email service. Sign up today.
SaaS Email Templates - Responsive HTML email templates for SaaS startups
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Email2Go.io - Perfect emails are born here
Constant Contact - Constant Contact offers email marketing, social media marketing, online survey, event marketing, digital storefronts, and local deals tools.