Plunk
Plunk is an open-source, self-hostable transactional email platform offering email sending, marketing campaigns, and workflow automation at $0.001 per email with unlimited contacts.
Plunk is an open-source email platform released under AGPL-3.0 that enables transactional emails, marketing campaigns, and workflow automation in a single self-hostable solution. The platform charges $0.001 per email with no contact limits, is GDPR compliant, EU-hosted, and has over 5,000 GitHub stars. It can be set up in under five minutes and is positioned as a replacement for Resend, SendGrid, Mailchimp, Customer.io, and Mailgun.