Plunk is an open-source email platform that brings transactional, marketing, and broadcast emails into a single developer-friendly tool. Built on AWS SES, it offers a REST API, SMTP relay, visual workflow automation, and contact management with unlimited contacts. You pay $0.001 per email with no contact-based fees, or self-host it for free. Plunk suits SaaS startups, developers, and technical teams who want cost control, EU data hosting, and freedom from vendor lock-in.

• Transactional Emails: Send emails from your app through a simple REST API with template support and variable substitution.
• Workflow Automation: Build advanced email sequences with triggers, delays, and conditional logic using a visual builder, no code required.
• Campaigns & Broadcasts: Send newsletters and product updates to large audiences with responsive templates or custom HTML.
• SMTP Relay: Use Plunk as an SMTP server to send emails from any existing tool or framework.
• Contact Management & Segments: Organize contacts with custom fields, full activity history, and dynamic filtering to target the right audience.
• Real-Time Analytics: Track opens, clicks, bounces, and unsubscribes with data feeding into each contact's timeline.
• Custom Domains: Verify and send from your own domains with DKIM, SPF, and DMARC authentication.
• Self-Hosting: Deploy your own instance via Docker under the AGPL-3.0 license for full data ownership.
• Inbound Emails: Receive and process incoming emails using custom routing rules and email handling workflows.

• Transparent Pricing: Flat $0.001 per email with unlimited contacts means predictable costs even as your list grows.
• Open Source: AGPL-licensed codebase lets you self-host, audit, and modify the platform to fit your needs.
• Unified Email Stack: One tool handles transactional, marketing, and broadcast emails, replacing multiple subscriptions.
• Developer-Friendly: Simple REST API, SMTP support, and SDKs make integration into SaaS apps quick and straightforward.
• EU Data Hosting: All data processed on EU servers, helping with GDPR compliance and data sovereignty needs.

• Self-Hosting Requires Technical Management: Running your own instance means managing uptime, updates, and deliverability yourself.
• Smaller Ecosystem: Fewer third-party integrations, SDKs, and community resources compared to SendGrid or Mailgun.
• Basic Analytics: Reporting covers essentials but lacks the depth of specialized analytics or advanced A/B testing platforms.
• Limited Enterprise Featuree: Large organizations may miss features commonly found in enterprise email platforms, such as dedicated IP management, formal SLAs, and extensive enterprise support options.
• AGPL License: The copyleft license may raise legal concerns for some commercial products embedding the code.

• SaaS Transactional Emails: Send welcome emails, password resets, receipts, and notifications straight from your app via the REST API. Ideal for startups needing reliable delivery without high per-contact fees.
• Product Newsletters: Create and schedule campaigns to update customers on new features, releases, and company news using the drag-and-drop editor or custom HTML.
• Onboarding Automation: Build multi-step welcome sequences with delays and conditions to guide new users through activation milestones without writing code.
• Waitlist & Launch Management: Collect signups, segment early adopters, and send timed announcements when your product launches or opens new features.
• Customer Re-Engagement: Create automated workflows that target inactive users with personalized follow-ups based on user activity, engagement, or custom events.
• Self-Hosted Email for Compliance: Deploy Plunk on your own servers when you need more control over hosting, data management, and privacy requirements.