Plunk website screenshot

Plunk

Plunk is an open-source (AGPL-3.0) email platform for SaaS that unifies transactional email, marketing campaigns, and event-driven automations behind a single REST API. The hosted service runs at api.useplunk.com with Bearer secret / public API keys, and the entire stack can be self-hosted with Docker Compose for full data ownership and no per-email costs.

Plunk publishes 4 APIs on the APIs.io network, including Campaigns API, Contacts API, Events API, and 1 more. Tagged areas include Email, Transactional Email, Marketing, Automation, and Open Source.

Plunk’s developer surface includes authentication, documentation, and 8 more developer resources.

🌐 Visit website 📡 Source on GitHub
40.6/100 thin ▬ flat Agent 37/100 agent ready Full breakdown ↓
scored 2026-08-05 · rubric v0.9.1
AccessFreemiumOpen⚡ Free to try
4 APIs
EmailTransactional EmailMarketingAutomationOpen SourceSaaS

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-05 · rubric v0.9.1
Composite quality — 40.6/100 · thin
Contract Quality 16.6 / 25
Developer Ergonomics 3.9 / 20
Commercial Clarity 7.9 / 20
Operational Transparency 4.8 / 13
Governance 0.0 / 12
Discoverability 7.4 / 10
Agent readiness — 37/100 · agent ready
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 7 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/plunk: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 4

Individual APIs this provider publishes, each with its own machine-readable definition.

Plunk Campaigns API

Create and send marketing campaigns.

Plunk Contacts API

Manage contacts and their subscription state.

Plunk Events API

Track contact events that drive automations.

Plunk Transactional API

Send transactional email.

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Plunk API

OPEN COLLECTION

Pricing Plans 1

Published pricing tiers and plan structures.

Plunk Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Plunk Rate Limits

3 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Plunk Finops

FINOPS

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Plunk Authentication

http · 1 scheme

SECURITY

Plunk Domain Security

TLSv1.3 · DMARC

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Plunk Agentic Access

14 operations · 11 acting

14 operations · 11 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity
 Authentication
Authentication

Operate 1

Status, limits, changes, and where to get help

RateLimits
RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans
Plans
 FinOps
FinOps

Company 2

The organization behind the API

LinkedIn
LinkedIn
 Website
Website

Source (apis.yml)

apis.yml Raw ↑ 
aid: plunk
url: https://raw.githubusercontent.com/api-evangelist/plunk/refs/heads/main/apis.yml
name: Plunk
kind: company
description: Plunk is an open-source (AGPL-3.0) email platform for SaaS that unifies transactional email, marketing campaigns,
  and event-driven automations behind a single REST API. The hosted service runs at api.useplunk.com with Bearer secret /
  public API keys, and the entire stack can be self-hosted with Docker Compose for full data ownership and no per-email costs.
accessModel:
  pricing: freemium
  onboarding: open
  trial: false
  try_now: true
  public: true
  label: Freemium · Open access
  confidence: high
  source:
  - plans
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/plunk.png
tags:
- Email
- Transactional Email
- Marketing
- Automation
- Open Source
- SaaS
created: '2026-06-20'
modified: '2026-06-20'
specificationVersion: '0.19'
apis:
- aid: plunk:plunk-campaigns-api
  name: Plunk Campaigns API
  description: Create and send marketing campaigns.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Campaigns
  properties:
  - type: OpenAPI
    url: openapi/plunk-campaigns-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-contacts-api
  name: Plunk Contacts API
  description: Manage contacts and their subscription state.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Contacts
  properties:
  - type: OpenAPI
    url: openapi/plunk-contacts-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-events-api
  name: Plunk Events API
  description: Track contact events that drive automations.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Events
  properties:
  - type: OpenAPI
    url: openapi/plunk-events-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-transactional-api
  name: Plunk Transactional API
  description: Send transactional email.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Transactional
  properties:
  - type: OpenAPI
    url: openapi/plunk-transactional-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
common:
- type: AgenticAccess
  url: agentic-access/plunk-agentic-access.yml
- type: DomainSecurity
  url: security/plunk-domain-security.yml
- type: Authentication
  url: authentication/plunk-authentication.yml
- type: GitHubOrganization
  url: https://github.com/useplunk
- type: LinkedIn
  url: https://www.linkedin.com/company/useplunk
- type: Website
  url: https://www.useplunk.com
- type: Documentation
  url: https://docs.useplunk.com
- type: Plans
  url: plans/plunk-plans-pricing.yml
- type: RateLimits
  url: rate-limits/plunk-rate-limits.yml
- type: FinOps
  url: finops/plunk-finops.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com