MailOptin

MailOptin is a WordPress lead-generation and email-automation plugin that converts website visitors into subscribers with popups, slide-ins, notification bars and inline optin forms, then sends one-off newsletters and event-triggered automated emails. It connects WordPress to more than sixty email marketing platforms, CRMs, form plugins, e-commerce and membership systems — Mailchimp, ActiveCampaign, HubSpot, AWeber, Klaviyo, Brevo, Salesforce, WooCommerce and others — and can post optin submissions to an arbitrary endpoint through a generic webhook connection. MailOptin is self-hosted software rather than a hosted service: it publishes no product API, no OpenAPI and no client SDK, and all functionality runs inside the customer's own WordPress installation. Its own website, mailoptin.io, runs WordPress and does serve a public self-describing REST API together with an OAuth-protected Model Context Protocol server.

MailOptin publishes 1 API on the APIs.io network. Tagged areas include Company, Email Marketing, Marketing Automation, Lead Generation, and WordPress.

The MailOptin catalog on APIs.io includes 1 event-driven AsyncAPI specification.

MailOptin’s developer surface includes documentation, getting-started guide, support, engineering blog, pricing, signup flow, changelog, and 19 more developer resources.

🌐 Visit website 📡 Source on GitHub
50.1/100 developing ▬ flat Agent 48/100 agent ready Full breakdown ↓
scored 2026-08-17 · rubric v0.11.0
1 APIs 1 MCP Servers
CompanyEmail MarketingMarketing AutomationLead GenerationWordPressNewslettersWebhooksModel Context ProtocolPlugins

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-17 · rubric v0.11.0
Composite quality — 50.1/100 · developing
Contract Quality 12.9 / 25
Developer Ergonomics 9.1 / 20
Commercial Clarity 15.3 / 20
Operational Transparency 3.8 / 13
Governance 1.5 / 12
Discoverability 7.6 / 10
Agent readiness — 48/100 · agent ready
Machine-Readable Contract 18 / 18
Agentic Access Contract 0 / 10
MCP Server 12 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 8 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 6 / 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/mailoptin: 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 1

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

MailOptin Site REST API and MCP Server

The WordPress REST API served by mailoptin.io, plus the Model Context Protocol server exposed through the WordPress MCP Adapter at the mcp namespace. The REST root is a public, ...

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

mailoptin-mcp.yml

MCP SERVER

Pricing Plans 1

Published pricing tiers and plan structures.

Mailoptin Plans Pricing

5 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Mailoptin Rate Limits

0 limits

RATE LIMITS

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Mailoptin Webhooks

ASYNCAPI

Security Posture 2

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

Mailoptin Authentication

3 schemes

SECURITY

Mailoptin Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Scopes 1

OAuth scopes governing access to this provider's APIs.

Mailoptin Scopes

OAuth 2.0 · no documented scopes

0 scopes

SCOPES

Resources

Get Started 2

Portal, sign-up, and the first successful call

GettingStarted
GettingStarted
 SignUp
SignUp

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 3

MCP servers, agent skills, and machine-readable catalogs

MCPServer
MCPServer
 WellKnown
WellKnown
 LLMsTxt
LLMsTxt

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Lifecycle
Lifecycle
 Webhooks
Webhooks
 Conformance
Conformance
 Conventions
Conventions
 ErrorCatalog
ErrorCatalog

Build 2

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization
 Packages
Packages

Access & Security 3

Authentication, authorization, and security posture

Authentication
Authentication
 OAuthScopes
OAuthScopes
 DomainSecurity
DomainSecurity

Operate 3

Status, limits, changes, and where to get help

Support
Support
 ChangeLog
ChangeLog
 RateLimits
RateLimits

Commercial 4

Pricing, plans, and the legal terms of use

Pricing
Pricing
 TermsOfService
TermsOfService
 PrivacyPolicy
PrivacyPolicy
 Plans
Plans

Company 3

The organization behind the API

Website
Website
 Blog
Blog
 BlogRSS
BlogRSS

Source (apis.yml)

apis.yml Raw ↑ 
aid: mailoptin
name: MailOptin
description: 'MailOptin is a WordPress lead-generation and email-automation plugin that converts website visitors into subscribers
  with popups, slide-ins, notification bars and inline optin forms, then sends one-off newsletters and event-triggered automated
  emails. It connects WordPress to more than sixty email marketing platforms, CRMs, form plugins, e-commerce and membership
  systems — Mailchimp, ActiveCampaign, HubSpot, AWeber, Klaviyo, Brevo, Salesforce, WooCommerce and others — and can post
  optin submissions to an arbitrary endpoint through a generic webhook connection. MailOptin is self-hosted software rather
  than a hosted service: it publishes no product API, no OpenAPI and no client SDK, and all functionality runs inside the
  customer''s own WordPress installation. Its own website, mailoptin.io, runs WordPress and does serve a public self-describing
  REST API together with an OAuth-protected Model Context Protocol server.'
image: https://mailoptin.io/wp-content/uploads/2014/05/mailoptin-plugin-banner.png
url: https://raw.githubusercontent.com/api-evangelist/mailoptin/refs/heads/main/apis.yml
x-type: company
x-source: harvest:marketing-integration-graph
specificationVersion: '0.20'
created: '2026-08-12'
modified: '2026-08-12'
tags:
- Company
- Email Marketing
- Marketing Automation
- Lead Generation
- WordPress
- Newsletters
- Webhooks
- Model Context Protocol
- Plugins
apis:
- aid: mailoptin-site
  name: MailOptin Site REST API and MCP Server
  description: The WordPress REST API served by mailoptin.io, plus the Model Context Protocol server exposed through the WordPress
    MCP Adapter at the mcp namespace. The REST root is a public, self-describing route index — 35 namespaces and 771 routes,
    each with its argument schema — and content routes under wp/v2 answer anonymously. The MCP endpoint is live but auth-gated,
    returning 401 mcp_unauthorized with a WWW-Authenticate Bearer challenge that links to RFC 9728 protected-resource metadata.
    This is the company website's own surface, not a product API for the MailOptin lead-generation service, which ships as
    a self-hosted WordPress plugin.
  humanURL: https://mailoptin.io/
  baseURL: https://mailoptin.io/wp-json
  tags:
  - WordPress
  - Model Context Protocol
  - OAuth
  properties:
  - type: MCPServer
    url: mcp/mailoptin-mcp.yml
  - type: Authentication
    url: authentication/mailoptin-authentication.yml
  - type: OAuthScopes
    url: scopes/mailoptin-scopes.yml
  - type: ErrorCatalog
    url: errors/mailoptin-problem-types.yml
  - type: Conventions
    url: conventions/mailoptin-conventions.yml
  - type: RateLimits
    url: rate-limits/mailoptin-rate-limits.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Website
  url: https://mailoptin.io/
- type: Documentation
  url: https://mailoptin.io/docs/
- type: GettingStarted
  url: https://mailoptin.io/section/getting-started/
- type: Support
  url: https://mailoptin.io/support/
- type: Blog
  url: https://mailoptin.io/blog/
- type: BlogRSS
  url: https://mailoptin.io/blog/feed/
- type: GitHubOrganization
  url: https://github.com/mailoptin
- type: Pricing
  url: https://mailoptin.io/pricing/
- type: SignUp
  url: https://my.mailoptin.io/login/
- type: TermsOfService
  url: https://mailoptin.io/terms-conditions/
- type: PrivacyPolicy
  url: https://mailoptin.io/privacy-policy/
- type: ChangeLog
  url: changelog/mailoptin-changelog.yml
- type: Lifecycle
  url: lifecycle/mailoptin-lifecycle.yml
- type: Plans
  url: plans/mailoptin-plans-pricing.yml
- type: RateLimits
  url: rate-limits/mailoptin-rate-limits.yml
- type: Packages
  url: packages/mailoptin-packages.yml
- type: Webhooks
  url: asyncapi/mailoptin-webhooks.yml
- type: Conformance
  url: conformance/mailoptin-conformance.yml
- type: Conventions
  url: conventions/mailoptin-conventions.yml
- type: ErrorCatalog
  url: errors/mailoptin-problem-types.yml
- type: Authentication
  url: authentication/mailoptin-authentication.yml
- type: OAuthScopes
  url: scopes/mailoptin-scopes.yml
- type: MCPServer
  url: mcp/mailoptin-mcp.yml
- type: WellKnown
  url: well-known/mailoptin-well-known.yml
- type: LLMsTxt
  url: llms/mailoptin-llms.txt
- type: DomainSecurity
  url: security/mailoptin-domain-security.yml
x-enrichment:
  date: '2026-08-12'
  status: enriched
  artifacts_added: 17
  pass: local-v1
x-coverage:
  state: covered
  reason: covered
  detail: MailOptin ships no product API, but mailoptin.io serves real machine-readable documents — RFC 8414 authorization-server
    metadata, RFC 9728 protected-resource metadata, a live OAuth-gated MCP server and a public 771-route WordPress REST index
    — all of which were fetched and recorded.
  evidence:
  - url: https://mailoptin.io/.well-known/oauth-protected-resource
    status: 200
  - url: https://mailoptin.io/wp-json/mcp/mcp-oauth-server
    status: 401
  checked: '2026-08-12'
x-vouched-by:
- Drip
- MailerLite
- SendPulse
x-vouch-count: 3