Mailly

mailly-mcp

The MCP server behind Mailly's connector, plus the Mailly plugin for Claude and Codex.

• src/: the MCP server, a Cloudflare Worker. It offers typed tools for Mailly mail, drafts, sending, domains, contacts, templates, campaigns, workflows and webhooks. Every tool calls the Mailly REST API with the caller's Mailly API key, so authentication, billing and workspace isolation all stay in the API.
• ui/: the MCP Apps UI (email and draft cards), bundled into ui:// resources. It is off unless MCP_APPS=1.
• plugins/mailly: the plugin for Claude (claude.ai, Cowork and Claude Code) and Codex. It points at the hosted server and adds a skill for working with email safely.
• plugins/openai/mailly: the public ChatGPT/Codex update package, based on the published 0.3.1 release, with its existing listing, review cases, demo link, skill, and PNG icon retained.

Use the hosted server

Add https://mcp.mailly.site/mcp as a remote MCP server and sign in with your Mailly account (OAuth). In ChatGPT, add the published Mailly plugin. In Claude Code you can install the plugin instead:

/plugin install mailly --marketplace superagents-lab/mailly-mcp

This server is an OAuth protected resource. Mailly's API (https://api.mailly.site/api/auth) is the authorization server: clients find it through /.well-known/oauth-protected-resource, sign the user in there, and send the access token here. The server passes the token, or an API key, unchanged to Mailly's REST API, which checks it and the scopes it carries. The tool list is narrowed to the same scopes (GET /me).

Keep ChatGPT and Codex connections authorized

The public OpenAI configuration in plugins/openai/mailly/mcp.json and the Codex compatibility configuration in plugins/mailly/.codex-plugin/mcp.json request offline_access in extensions.com.openai.auth.baseScopes. Mailly issues a refresh token only when that scope is granted. Resource discovery and tool scopes describe Mailly data permissions; they do not request offline access on the client's behalf. Without it, sign-in succeeds but access ends when the one-hour access token expires.

For a published OpenAI plugin, upload the updated plugin package to the existing plugin, confirm that the saved MCP authentication settings include offline_access, then reconnect the account and rescan. Deploying the Worker alone does not update those saved settings. Reconnecting with the old settings will still produce a connection without a refresh token. For manually configured clients, include offline_access alongside the desired Mailly scopes when starting OAuth authorization.

Package the contents of plugins/openai/mailly as the upload root. Do not include the repository, marketplace, or the installed plugin's Portal-generated .app.json and apps binding in a public upload. Keep those generated bindings in the installed release; the submission portal owns them. The package version is 0.3.2. Separately, the Worker declares all three tool annotation booleans explicitly, including destructiveHint: false for read-only tools; that server update requires a Worker deployment and rescan. The MCP Registry listing is unchanged.

Run it yourself

npm installnpm run dev          # wrangler dev on http://localhost:8787/mcp

Call /mcp with Authorization: Bearer <your Mailly API key> (from https://mailly.site/app/developers). Without the MAILLY_API service binding it calls MAILLY_API_URL (default https://api.mailly.site) over the internet. To host your own copy, change the mcp.mailly.site route in wrangler.jsonc. OAuth sign-in only works at https://mcp.mailly.site/mcp, because Mailly issues tokens for that resource; elsewhere use an API key.

Develop

npm run typechecknpm test             # builds dist/worker.js and runs it in Miniflare against a stub API

The Mailly server repository runs its OAuth and end-to-end tests against dist/worker.js from a sibling checkout of this repository.

server.json is the listing in the MCP Registry as site.mailly/mcp. The site.mailly namespace is proven by a DNS TXT record on mailly.site, so publish with mcp-publisher login dns --domain mailly.site --private-key <key> and mcp-publisher publish from a machine that holds the key. Bump version for each release.

License

MIT