Plunk

Plunk is the open-source email platform that does what Resend won't — transactional and marketing emails in one tool. Built on AWS SES, it handles campaign broadcasts, workflow automation, and triggered emails alongside your transactional sends. Self-host it and pay $0.001 per email through SES instead of per-subscriber pricing.

If you're an indie hacker sending both product emails and marketing campaigns, Plunk consolidates two tools into one. Resend has a better developer experience and React Email templates but only does transactional. Listmonk is the lightweight newsletter alternative without transactional support. SendGrid does both but at enterprise pricing.

The catch: Plunk is AGPL-3.0 — your modifications must be open-sourced if you distribute them. The project is younger and less battle-tested than Listmonk or Nodemailer. The documentation is thinner. And building on AWS SES means you inherit SES's deliverability management — sandbox mode, domain verification, reputation monitoring are all your responsibility.