Mailivery - Reach the Inbox, not the spam folder.
thankme - Create a thank-you page for anyone and express gratitude
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.
GiveThanksNow - Send thank you notes to COVID-19 frontline workers
Postal - Open source mail delivery platform, alternative to Mailgun or Sendgrid
NumWorks - The graphing calculator that makes learning math easier.