Best open-source alternatives to Listmonk

Plunk is an open-source email platform intended for developers and teams that want to send emails from their own applications without relying entirely on hosted email SaaS products. It positions itself as a self-hosted alternative to services such as SendGrid, Resend, and Mailgun. The project supports transactional email sending, newsletter campaigns, workflow automations, contact management, and analytics. The README indicates that self-hosting is primarily done through a Docker image, and it links to deployment documentation for a full guide. The platform is built on top of AWS SES, so that service is part of its operating model.