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useplunk/plunk

Open-source, self-hostable email platform for transactional emails, marketing campaigns, and workflow automation, positioned as an alternative to SendGrid, Resend, and Mailgun.

Open-source alternative to:SendGridResendMailgun

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5,540
Forks
420
Open issues
53
Last commit
3 days ago

What is it?

Plunk is an email platform that combines transactional email sending, marketing campaigns, and workflow automation in one product. It can be self-hosted, and the project's pricing is described as $0.001 per email with no contact limits.

Developers can send emails directly through an API with template support and variable substitution, or use Plunk as an SMTP relay so existing tools and frameworks can send through it. For marketing, it supports newsletters to large audiences, dynamic contact segments, and automations built from triggers, delays, and conditional logic.

The platform also covers contact management with custom fields and activity history, real-time tracking of opens, clicks, bounces, and engagement, custom sending domains with DKIM and SPF support, and routing for inbound emails. The easiest way to deploy it is the official Docker image.

Key features

  • 01Sends transactional emails via API with templates and variable substitution.
  • 02Works as an SMTP relay for existing tools and frameworks.
  • 03Runs newsletter campaigns and workflow automations with triggers and delays.
  • 04Tracks opens, clicks, bounces, and engagement in real time.
  • 05Supports custom sending domains with DKIM and SPF.
  • 06Processes inbound emails with custom routing rules.

Use cases

  • Sending password resets, receipts, and notifications from a web application.
  • Replacing a hosted email service with a self-hosted instance to control costs and data.
  • Running newsletters and product update emails to a large contact list.
  • Routing email from legacy applications through an SMTP relay.

Quick start

  1. 1

    Pull the latest plunk Docker image from GitHub Container Registry

  2. 2

    Follow the self-hosting guide in the official documentation

Things to know

  • Licensed under AGPL-3.0, a copyleft license that requires sharing modified source code when offered as a network service.
  • Self-hosting requires setting up your own infrastructure, with the README pointing to a separate deployment guide.

In collections

Self-hosted apps

Topics

#email#transactional-email#smtp#email-marketing#self-hosted#automation#newsletter

FAQ

What is plunk?
Open-source, self-hostable email platform for transactional emails, marketing campaigns, and workflow automation, positioned as an alternative to SendGrid, Resend, and Mailgun. Plunk is an email platform that combines transactional email sending, marketing campaigns, and workflow automation in one product. It can be self-hosted, and the project's pricing is described as $0.001 per email with no contact limits.
Is plunk free to use? What license does it have?
plunk is open source under the AGPL-3.0 license. Check the license terms before using it in commercial products.
Is plunk still maintained?
Actively maintained. The last commit to plunk was on Oct 21, 2026.
What can I use plunk for?
Sending password resets, receipts, and notifications from a web application. Replacing a hosted email service with a self-hosted instance to control costs and data. Running newsletters and product update emails to a large contact list. Routing email from legacy applications through an SMTP relay.
How do I install plunk?
Pull the latest plunk Docker image from GitHub Container Registry Follow the self-hosting guide in the official documentation
Where can I get plunk?
The source code and installation instructions are on GitHub: https://github.com/useplunk/plunk

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