Plunk

What our check kept, up to 60 lines or 6 KB

# *
User-agent: *
Allow: /

# Host
Host: https://www.useplunk.com

# Sitemaps
Sitemap: https://www.useplunk.com/sitemap.xml

How we test this:

• We read robots.txt and check it doesn't disallow / for the agents that fetch for a user or find sites for AI search: ChatGPT-User, OAI-SearchBot, Claude-User, Claude-SearchBot, Perplexity-User, PerplexityBot (no robots.txt counts as allowed).
• We show blocks on GPTBot (OpenAI model training), not scored; ClaudeBot (Anthropic model training), not scored; Google-Extended (Gemini training and grounding), not scored in v1; CCBot (Common Crawl's open dataset), not scored: blocking them is the site's own call.
• Whether Google-Extended should be scored is a rubric v2 question, and we'll announce it before changing anything.
• Then we fetch your homepage as LeaderfileBot and check it returns 2xx after redirects, with no challenge page.

How we test this:

• We fetch your homepage and your docs page as LeaderfileBot, our own scanner, and check neither answers with a challenge page, or a 401 or 403 that a normal browser gets past.
• One blocked page is a fail; both caps your score at 39.
• Firewalls often let in crawlers they can verify, so ChatGPT or Claude may still get in where our scanner can't.

How we test this:

• We look for your docs page: the first homepage link to a docs., dev. or developer(s). subdomain of your domain, or to a /docs or /developer(s) path; with none, we try https://docs.<host>/ then https://<host>/docs.
• It passes if that page returns 200.
• Board companies use a docs URL we confirmed by hand.

How we test this:

• We read your homepage and your docs page and look for a pointer to an llms.txt: a link to it, a <link> tag, a Link header with rel="llms-txt" or an X-Llms-Txt header, or a line on the page naming /llms.txt.
• It passes when one points at an llms.txt that answers with markdown links.
• AFDocs checks the same (llms-txt-directive).

What our check kept, up to 60 lines or 6 KB

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap><loc>https://www.useplunk.com/sitemap-0.xml</loc></sitemap>
</sitemapindex>

How we test this:

• We fetch the Sitemap: URL from robots.txt, else /sitemap.xml, and check it returns 200 with a <urlset> or <sitemapindex> root element.

How we test this:

• We count the visible words in the raw HTML (no JavaScript run) of your homepage and your docs page, and check each has at least 150.
• With no docs page found (AR-FIND-02), the homepage is judged alone.

How we test this:

• We read your docs page and up to 7 more docs pages (the ones we read for other checks, then links on your docs page).
• A page fails when it answers 401 or 403 to a normal browser too, redirects to a sign-in page, or is a sign-in form with little else on it.
• A redirect counts as a sign-in when it adds one: a sign-in path the page didn't have, a login subdomain, or an identity provider's site such as Okta's when the page was on another site.
• A sign-up page, one whose title or main heading says sign up or create an account, isn't a login.
• A refusal only to automated readers is our scanner being blocked, not a login.
• A login on your docs page caps your score at 39; across the pages, a share of 25% or less caps it at 39, 50% or less at 59.

How we test this:

• We fetch /leaderfile-check-404, a page that shouldn't exist, and check it returns 404 or 410 after redirects.
• Off the board, if that address refuses automated readers, we try /leaderfile-check-404.html.

What our check kept, up to 60 lines or 6 KB

# Plunk

> Plunk is an open-source, all-in-one email platform for developers. It unifies marketing, transactional, and broadcast email behind a single API — built to handle millions of contacts with workflows, segments, templates, and deliverability tooling out of the box.

Plunk can be used as a hosted service at useplunk.com or self-hosted via Docker. Source code lives at https://github.com/useplunk/plunk.

Pages listed below with a `.md` suffix serve a Markdown version (also available by requesting the same URL with `Accept: text/markdown`). Other pages are HTML only.

For full product documentation, see the docs site: https://docs.useplunk.com/llms.txt

## Product

- [Plunk home](https://www.useplunk.com/index.md): Product overview, features, and positioning
- [Pricing](https://www.useplunk.com/pricing.md): Plans, included volume, and overage pricing
- [Made by humans](https://www.useplunk.com/made-by-humans): The team and story behind Plunk
- [EU hosting and GDPR](https://www.useplunk.com/eu): Where data is stored, sub-processors, and the DPA
- [Open-source email platform](https://www.useplunk.com/open-source-email-platform): License, self-hosting with Docker, and how Plunk compares to other open-source email tools
- [Amazon SES dashboard](https://www.useplunk.com/aws-ses): Plunk as the dashboard and platform on top of Amazon SES

## Features

- [Transactional email](https://www.useplunk.com/features/transactional-email): Send email from your app with one API call
- [Campaigns](https://www.useplunk.com/features/campaigns): Newsletters and product updates to a list, segment, or filter
- [Email editor](https://www.useplunk.com/features/email-editor.md): Drag-and-drop and code-based template editor
- [Workflows](https://www.useplunk.com/features/workflows.md): Event- and segment-triggered automation flows
- [Segments](https://www.useplunk.com/features/segments.md): Dynamic and static contact segments
- [SMTP](https://www.useplunk.com/features/smtp.md): Send through Plunk over standard SMTP
- [Inbound email](https://www.useplunk.com/features/inbound-email.md): Receive email at your verified domain and turn it into events

## Comparisons

- [Plunk vs Resend](https://www.useplunk.com/vs/resend)
- [Plunk vs SendGrid](https://www.useplunk.com/vs/sendgrid)
- [Plunk vs Mailchimp](https://www.useplunk.com/vs/mailchimp)
- [Plunk vs Mailgun](https://www.useplunk.com/vs/mailgun)
- [Plunk vs Postmark](https://www.useplunk.com/vs/postmark)
- [Plunk vs Customer.io](https://www.useplunk.com/vs/customerio)
- [Plunk vs Loops](https://www.useplunk.com/vs/loops)
- [Plunk vs Brevo](https://www.useplunk.com/vs/brevo)
- [Plunk vs ActiveCampaign](https://www.useplunk.com/vs/activecampaign)
- [Plunk vs Klaviyo](https://www.useplunk.com/vs/klaviyo)
- [Plunk vs ConvertKit](https://www.useplunk.com/vs/convertkit)
- [Plunk vs Bento](https://www.useplunk.com/vs/bento)
- [Plunk vs MailerLite](https://www.useplunk.com/vs/mailerlite)
- [Plunk vs Amazon SES](https://www.useplunk.com/vs/amazon-ses)
- [Plunk vs Mailjet](https://www.useplunk.com/vs/mailjet)
- [Plunk vs Buttondown](https://www.useplunk.com/vs/buttondown)
- [Plunk vs useSend](https://www.useplunk.com/vs/usesend)
- [Plunk alternatives](https://www.useplunk.com/alternatives/plunk): When another tool is the better choice
- [Resend alternatives](https://www.useplunk.com/alternatives/resend)
- [SendGrid alternatives](https://www.useplunk.com/alternatives/sendgrid)
- [Mailgun alternatives](https://www.useplunk.com/alternatives/mailgun)
- [Mailchimp alternatives](https://www.useplunk.com/alternatives/mailchimp)
- [Loops alternatives](https://www.useplunk.com/alternatives/loops)
- [Postmark alternatives](https://www.useplunk.com/alternatives/postmark)
- [Customer.io alternatives](https://www.useplunk.com/alternatives/customerio)
- [All comparisons](https://www.useplunk.com/vs)

## Guides

How we test this:

• We read llms.txt at your site root and, if your docs live on another host, at your docs root, and check one returns 200, isn't HTML and has at least one markdown link.
• Off the board, we also try your docs. host and /docs/llms.txt.
• We read the first 2 MB: a larger file is judged on that part, and the result says "read the first 2 MB; the file is larger".

How we test this:

• We read the llms.txt AR-READ-07 passes on (the first with markdown links) and fetch up to 12 of its links, spread through the file, two at a time.
• A link is broken when it answers 404 or 410, or its host doesn't exist.
• A 2xx after redirects resolves, and so does an answer like 400, 405 or 406 that shows the address is there (an MCP endpoint answers a plain GET with 405).
• A refusal, a 429 or a server error isn't judged.
• The credit is the share that resolve, halved when the file runs to 50,000 characters or more, and nothing past 100,000: AFDocs' size bands.
• With no llms.txt it isn't counted: AR-READ-07 counts that.

How we test this:

• On each docs page we read (up to 7) we count the characters of visible text in the raw HTML, and of its Markdown copy if it has one, and judge the page by the larger of the two: an agent reading either may be cut off.
• Under 50,000 passes, up to 100,000 is half, more fails: AFDocs' bands, from the limits agents cut pages at.
• The credit is the average across the pages.

What our check kept, up to 60 lines or 6 KB

<meta name="description" content="Send transactional emails, run marketing campaigns, and automate workflows. Open-source and self-hostable, $0.001 per email, no contact limits." data-next-head=""/>

How we test this:

• We check your homepage's raw HTML (no JavaScript run) has a non-empty meta description or og:description.

What our check kept, up to 60 lines or 6 KB

<h1>Welcome to Plunk</h1>
<h2>What is Plunk?</h2>
<h2>Key Features</h2>
<h3>Transactional Emails</h3>
<h3>Email Campaigns</h3>
<h3>Marketing Automation</h3>
<h3>Contact Management</h3>
<h3>Dynamic Segmentation</h3>
<h3>Email Templates</h3>
<h3>Event Tracking</h3>

How we test this:

• We check your docs page's raw HTML (no JavaScript run) has at least 2 headings (h1 to h3) with text and at least 150 visible words.
• Off the board, a docs page that comes back as markdown counts # to ### lines outside code blocks as its headings.

What our check kept, up to 60 lines or 6 KB

```bash

How we test this:

• On your docs surface, we look for a code block that carries a language tag: language-* or lang-* on <pre> or <code>, code-language-* on any element (a code block's wrapper, say), or a data-language or data-lang attribute.
• In markdown files, a fenced block with a language (```ts) counts.
• If no page shows one, we read the markdown copy each HTML page declares (a <link rel="alternate" type="text/markdown">, or its URL plus .md listed in your llms.txt), since many docs sites add the language label with JavaScript.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.

What our check kept, up to 60 lines or 6 KB

Plunk Pricing | The Open-Source Email Platform Plunk Features By humans Pricing Docs 5k Sign in Start for free Open main menu Simple, transparent pricing Free plan: 1,000 emails per month. Paid plan: $0.001 per email. Unlimited contacts, no hidden fees. Free f

How we test this:

• We fetch the first homepage link with 'pricing' in its path, else /pricing (board companies: a pricing URL we confirmed by hand), and check it returns 200 and its raw text (no JavaScript run) shows a price or 'free' within 80 characters of month, mo, year or yr.
• Off the board, a pricing address that answers with JSON counts when it has a price field.

What our check kept, up to 60 lines or 6 KB

# Welcome to Plunk (/)

## What is Plunk?

Plunk is an open-source email platform designed for developers who need a powerful, scalable solution for transactional and marketing emails. Built to handle millions of contacts, it provides everything you need to manage your email communications — sending, automation, segmentation, deliverability, and analytics.

## Key Features

<Cards>
  <Card title="Transactional Emails" href="/concepts/transactional-emails">
    Send transactional emails via API with template support and variable substitution
  </Card>

  <Card title="Email Campaigns" href="/concepts/campaigns">
    Create and send one-time email broadcasts to your contacts with advanced scheduling
  </Card>

  <Card title="Marketing Automation" href="/concepts/workflows">
    Build automated email sequences with visual workflow builder and conditional logic
  </Card>

  <Card title="Contact Management" href="/concepts/contacts">
    Manage millions of contacts with custom fields and CSV import capabilities
  </Card>

  <Card title="Dynamic Segmentation" href="/concepts/segments">
    Create dynamic audience segments based on contact data and behavior
  </Card>

  <Card title="Email Templates" href="/concepts/templates">
    Create reusable email templates for transactional and marketing emails
  </Card>

  <Card title="Event Tracking" href="/guides/tracking">
    Track events and use them to trigger workflows and segment audiences
  </Card>

  <Card title="Billing" href="/concepts/billing">
    Understand Plunk's billing model and pricing
  </Card>
</Cards>

## Quick Links

<Cards>
  <Card title="API Reference" href="/api-reference/overview">
    Explore the complete API documentation
  </Card>

  <Card title="Self-Hosting" href="/self-hosting/introduction">
    Deploy Plunk on your own infrastructure
  </Card>

  <Card title="Domain Verification" href="/guides/verifying-domains">
    Learn how to verify your domains for sending emails
  </Card>

  <Card title="API Keys" href="/guides/api-keys">
    Manage your API keys and authentication
  </Card>

How we test this:

• On each docs page we read (up to 7), one Markdown answer with content passes the page: it answers Accept: text/markdown with text/markdown, declares a copy with <link rel="alternate" type="text/markdown"> that returns Markdown, or the address the page lands on, after redirects, ending in .md does (for one ending in a slash, both /page.md and /page/index.md).
• An empty answer doesn't count.
• The credit is the share of pages that pass.
• AFDocs, Cloudflare's isitagentready and is-agentic check it.

What our check kept, up to 60 lines or 6 KB

{"@context":"https://schema.org","@type":"Organization","name":"Plunk","alternateName":"UsePlunk","url":"https://www.useplunk.com","logo":"https://www.useplunk.com/assets/logo.png","sameAs":["https://x.com/useplunk","https://github.com/useplunk/plunk"]}

How we test this:

• We check your homepage's raw HTML has an application/ld+json block that parses as JSON and has @type or @context.

How we test this:

• We fetch five standard .well-known files and check at least one returns 200 with valid JSON: oauth-authorization-server (RFC 8414), oauth-protected-resource (RFC 9728), openid-configuration, api-catalog (RFC 9727) and agent-card.json (A2A).
• This list is ours: AgentReady v2.0 doesn't name one.
• Off the board, on a miss, we also read oauth-protected-resource on the mcp., api. and docs. hosts of your domain, where that metadata usually lives, and it counts only with its resource field.

What our check kept, up to 60 lines or 6 KB

orkflow_execution Writing: plunk_create_contact , plunk_update_contact , plunk_subscribe_contact , plunk_unsubscribe_contact , plunk_delete_contact , plunk_send_email , plunk_reschedule_email , plunk_cancel_email , plunk_track_event , plunk_create_template , plunk_create_campaign , plunk_test_campaign , plunk_send_

How we test this:

• Passes when AR-ACT-03 passes (your docs surface names your own MCP server, not just a mention or a blog post about one; on the board, only an MCP server with a tool that acts on the product: send, manage or query, not only search docs, since AgentReady calls this "the interface an agent acts through"), or when your docs surface shows a CLI install: brew install, npm i -g, npm install -g, pipx install, uv tool install, go install, az extension add, or curl ... | sh (or | bash).
• A mention of MCP that isn't your own server, with no CLI install, isn't counted.
• For board companies, the CLI half counts only a command of the product's own CLI that we confirmed by hand, like az communication email send or twilio email:send, on the pages we read or on the docs page that shows it: an install alone could be any tool (an MCP setup guide installing pnpm, say).
• For a product inside a larger platform, the platform's MCP server or CLI counts when its docs show it covers the product.
• An MCP server earns both this check and AR-ACT-03, because AgentReady lists them as two items.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.

How we test this:

• We look for an OpenAPI or Swagger document: for board companies, a URL we confirmed by hand; then up to 2 links on your docs surface whose URL mentions openapi or swagger, or whose link text does for a .json or .yaml file (files on other sites count when your docs link them; an address written out in your llms.txt or another text file counts as a link, and its line as the link text); then /openapi.json and /openapi.yaml on your host and your docs host.
• Off the board, a .json or .yaml link under an llms.txt heading that names OpenAPI counts as a link to a spec, or, where that section has none, a link with no file extension, and on a miss we also try those two on the docs., developers. and api. hosts of your domain.
• It passes if one parses as JSON or YAML with an openapi or swagger key and at least one path.
• A spec over 10 MB counts as couldn't check.

How we test this:

• On your docs surface we look for an npm install (npm, yarn, pnpm or bun) and a pip install (pip, poetry or uv) of a named package.
• Both must appear, on any of the pages (AgentReady: npm and PyPI).
• Off the board, uv tool install and pipx install also count as a pip install.
• Off the board, if one is missing we also read the markdown copy each HTML page declares (a <link rel="alternate" type="text/markdown">, or its URL plus .md listed in your llms.txt), then up to 2 pages your llms.txt names for that language.
• AgentReady v2.0 asks for SDKs and a CLI here; this check tests the npm and PyPI half, and a CLI counts under AR-ACT-10.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.

What our check kept, up to 60 lines or 6 KB

ocumentation Copy Markdown Open Reading this with electronic eyes? Add .md for the Markdown cut. Base URL https://next-api.useplunk.com All API requests use this base URL. Authentication Include your API key in the Authorization header: Authorization: Bearer YOUR_API_KEY Secret Key (sk_*) — Required for all endpoints except /v1/track Public Key (pk_*) — Only works with /v1/track for client-side event tra

How we test this:

• A stand-in: AgentReady asks for self-serve key generation with documented scopes, or OAuth metadata, and key sign-up can't be tested in code.
• It passes if OAuth metadata parses as JSON with the field its RFC requires (issuer for RFC 8414, resource for RFC 9728), or if your docs say "API key" or "API token" (also inside a placeholder like YOUR_API_KEY) within 200 characters of a documented auth header: an X-...-Key or X-...-Token header, a header named ...-Key or ...-Token, Authorization with Bearer, or "Bearer API key".
• The word "token" on its own doesn't count.
• For board companies we also read the authentication page their docs link.
• Off the board, OAuth metadata with its resource field on your mcp., api. or docs. host also counts.
• A board company whose API signs each request (like AWS Signature Version 4) or takes the key in the request body isn't counted: this stand-in can't judge that kind of auth either way.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.

How we test this:

• In the OpenAPI spec AR-ACT-02 finds, we count the operations with a non-empty operationId.
• The credit is the share that have one.
• With no spec, it isn't counted: AR-ACT-02 already counts that.

What our check kept, up to 60 lines or 6 KB

orkflow_execution Writing: plunk_create_contact , plunk_update_contact , plunk_subscribe_contact , plunk_unsubscribe_contact , plunk_delete_contact , plunk_send_email , plunk_reschedule_email , plunk_cancel_email , plunk_track_event , plunk_create_template , plunk_create_campaign , plunk_test_campaign , plunk_send_

How we test this:

• On your docs surface we look for your own MCP server and quote the line: your name next to "MCP" ("Acme MCP server"), "our" or "official" MCP server, or an mcp.<your domain> address.
• Any other mention of "MCP server" or "Model Context Protocol", like a directory or an explainer, isn't counted: it can't fail you and it earns no points, because we can't tell the server is yours.
• A mention in a link to a blog post, or on an llms.txt line that links to one, doesn't count at all: a post about building a server isn't one you ship.
• For board companies we read the MCP page their docs link and list the tools it documents: a server that only searches your docs counts here, as AgentReady describes an MCP server as a "standard tool protocol for docs search and actions".
• We don't probe /mcp or call any server.
• Off the board, OAuth metadata with its resource field on your mcp. host also counts: it's the server's own file.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.

How we test this:

• In the OpenAPI spec AR-ACT-02 finds, we count the operations that declare a 4xx, 5xx or default response with a schema, directly or through a $ref.
• The credit is the share that do.
• We note when they use application/problem+json (RFC 9457), the standard shape.
• With no spec, it isn't counted.
• The IETF's draft agent-friendly API profile, is-agentic and Alpic check it.

How we test this:

• We check your homepage's raw HTML, inline scripts included, contains modelContext (AgentReady names document.modelContext).
• External scripts aren't fetched.

How we test this:

• Any of three passes: /.well-known/agent-skills/index.json on your site or your docs (or one a Link header names) lists a skill whose file answers; your docs or llms.txt link a SKILL.md that answers with a name and a description; or your docs show a skills install command, on a page we read or on up to 3 pages your docs or llms.txt link about skills or your CLI.
• An install is npx skills add, claude plugin install, a git clone into a skills folder, or your own command line running plugin install or skills add right after the word skill.
• An index under a folder, like /developer/, may list its files from that folder.
• Cloudflare's isitagentready, agenticplug and Alpic check it.

How we test this:

• We look for OAuth authorization server metadata (RFC 8414): at /.well-known/oauth-authorization-server on your site, through the authorization_servers your protected-resource metadata (RFC 9728) names, and on your mcp. host.
• It passes when it lists S256 in code_challenge_methods_supported, has scopes_supported, and has a registration_endpoint or client_id_metadata_document_supported, as the MCP authorization spec asks.
• With no OAuth metadata, it isn't counted.

How we test this:

• On your docs surface we look for an install in each of four languages: TypeScript/JavaScript (npm, yarn, pnpm or bun), Python (pip, poetry or uv), Go (go get) and Java (a Maven <artifactId> or a Gradle implementation line).
• All four must appear.
• This shows how to install, not that a package is official.
• If none of the pages we read is a quickstart or SDK page, a miss isn't counted: it can't fail you or withhold your score.
• Ours, not AgentReady's.

How we test this:

• In the OpenAPI spec AR-ACT-02 found, we look for a POST operation on a path containing mail, email, message or send.
• No spec counts as a fail.
• Ours, not AgentReady's.

What our check kept, up to 60 lines or 6 KB

The Open-Source Email Platform Plunk Features By humans Pricing Docs 5k Sign in Start for free Open main menu Simple, transparent pricing Free plan: 1,000 emails per month. Paid plan: $0.001 per email. Unlimited contacts, no hidden fees. Free forever 1,000 emails / mo No credit card required Transactional emails Workflo

How we test this:

• On the pricing page AR-READ-11 reads, we look for "free" within 300 characters of a number followed by emails, messages or sends and a period (a month, a day, or 30 days), like "3,000 emails/month" or "4,000 sends in any rolling 30-day window", in the raw text (no JavaScript run).
• A one-time allowance with no period doesn't count.
• Ours, not AgentReady's.