MailKite for Ruby

Email for every product you ship — receive email as a webhook, send over a verified domain, give an AI agent its own inbox.
The official MailKite library for Ruby.

Docs · Library guide · mailkite.dev · AI agents

Read-only mirror. This repo is a generated, release-time mirror of the MailKite monorepo (the private source of truth) — development doesn't happen here. Install from RubyGems and open issues against the MailKite docs.

gem install mailkite

require "mailkite"

mk = Mailkite::Client.new(ENV["MAILKITE_API_KEY"])

res = mk.send(
  "from" => "hello@myapp.ai",
  "to" => "ada@example.com",
  "subject" => "Your invoice #1042",
  "html" => "<p>Thanks! Receipt attached.</p>"
)

The gem ships a :mailkite delivery method — point ActionMailer at it and every existing mailer delivers through the MailKite API, no SMTP credentials:

# config/environments/production.rb
config.action_mailer.delivery_method = :mailkite
config.action_mailer.mailkite_settings = { api_key: ENV["MAILKITE_API_KEY"] }

Your mailers don't change:

class InvoiceMailer < ApplicationMailer
  def paid(invoice)
    attachments["invoice-#{invoice.number}.pdf"] = invoice.pdf
    mail from: "billing@myapp.ai", to: invoice.customer_email,
         subject: "Your invoice #{invoice.number}"
  end
end

Outside Rails, register it on the mail gem directly:

require "mailkite"

Mail.defaults { delivery_method Mailkite::DeliveryMethod, api_key: ENV["MAILKITE_API_KEY"] }

The mail gem is not a dependency of mailkite — it's required only when the delivery method is instantiated. Features the send API can't express (custom headers, inline cid: images) raise Mailkite::DeliveryMethod::UnsupportedFeatureError instead of silently dropping them.

Runnable examples live in examples/ — send mail, verify webhooks, build an AI email agent, and log users in:

Every method is documented on its own page under docs/. The full surface:

MailKite speaks the Model Context Protocol: every API method is a tool your AI assistant (Claude, Cursor, …) can call — send mail, manage domains, search the docs, and give an agent its own inbox. Full guide: https://mailkite.dev/docs/ai-agents.

Hosted (recommended) — one-click OAuth, no key to copy:

claude mcp add --transport http mailkite https://mcp.mailkite.dev/mcp

In Claude Code you can also install the plugin:

/plugin marketplace add mailkite/claude-code
/plugin install mailkite@mailkite

Any chat/UI agent: "Add the MCP server at https://mcp.mailkite.dev/mcp and authenticate in the browser when prompted."

Local (static key, offline / CI):

{ "mcpServers": { "mailkite": { "command": "npx", "args": ["-y", "@mailkite/mcp"], "env": { "MAILKITE_API_KEY": "mk_live_…" } } } }

Give an agent its own inbox. Route inbound mail to a built-in inbox agent (the agent route action) and it answers, files, or escalates on its own — see https://mailkite.dev/docs/ai-agents.

Same contract, every language — pick the one for your stack (full list: https://mailkite.dev/docs/libraries):

• 📚 Documentation: https://mailkite.dev/docs
• 📦 This library's guide: https://mailkite.dev/docs/libraries
• 🤖 AI agents (MCP + inbox agents): https://mailkite.dev/docs/ai-agents
• 🌐 Website: https://mailkite.dev
• 🧭 All libraries: https://mailkite.dev/docs/libraries

_{Generated from the shared MailKite API contract. © MailKite.}