SaaS Email Templates - Responsive HTML email templates for SaaS startups
Mailivery - Reach the Inbox, not the spam folder.
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Sidemail - The simplest way to send transactional emails. Sidemail makes sending transactional emails trivial, it's perfect for side projects, MVPs or the next big thing.
Email Template Generator - Email templates for your important relationships
Postal - Open source mail delivery platform, alternative to Mailgun or Sendgrid