Add AgentMail third-party MCP plugin (#211)

Wire AgentMail's hosted MCP server into the marketplace using the documented Cursor API-key path (x-api-key header).

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Sam Sokolin <SamSokolin@users.noreply.github.com>

.cursor-plugin/marketplace.json

@@ -159,6 +159,11 @@
       "name": "navan",
       "source": "third_party/navan",
       "description": "Connect to Navan — query expenses, analyze travel bookings, check policies and approvals, and manage cards — via Navan's official remote MCP server."
+    },
+    {
+      "name": "agentmail",
+      "source": "third_party/agentmail",
+      "description": "Connect to AgentMail — create inboxes, send and receive email, search threads, and manage drafts and attachments — via AgentMail's official hosted MCP server."
     }
   ]
 }

README.md

@@ -30,6 +30,7 @@ Official Cursor plugins for popular developer tools, frameworks, and SaaS produc
 | `docusign` | [Docusign](third_party/docusign/) | Cursor | Integrations | Connect to Docusign — work with eSignature envelopes and templates, Maestro workflows, and Navigator agreements — via Docusign's official remote MCP server (beta). |
 | `x` | [X](third_party/x/) | Cursor | Integrations | Read-only access to the X API — search posts and users, read timelines and mentions, and pull trends and news — via X's official hosted MCP server. |
 | `navan` | [Navan](third_party/navan/) | Cursor | Integrations | Connect to Navan — query expenses, analyze travel bookings, check policies and approvals, and manage cards — via Navan's official remote MCP server. |
+| `agentmail` | [AgentMail](third_party/agentmail/) | Cursor | Integrations | Connect to AgentMail — create inboxes, send and receive email, search threads, and manage drafts and attachments — via AgentMail's official hosted MCP server. |
 Author values match each plugin’s `plugin.json` `author.name` (Cursor lists `plugins@cursor.com` in the manifest).
 
 ## Repository structure

third_party/agentmail/.cursor-plugin/plugin.json

@@ -0,0 +1,47 @@
+{
+  "name": "agentmail",
+  "displayName": "AgentMail",
+  "version": "1.0.0",
+  "minClientVersions": {
+    "cursor": "3.13.0"
+  },
+  "description": "Connect to AgentMail — create inboxes, send and receive email, search threads, and manage drafts and attachments — via AgentMail's official hosted MCP server.",
+  "author": {
+    "name": "Cursor",
+    "email": "plugins@cursor.com"
+  },
+  "homepage": "https://www.agentmail.to/docs/integrations/mcp",
+  "repository": "https://github.com/cursor/plugins",
+  "license": "MIT",
+  "logo": "assets/logo.png",
+  "keywords": [
+    "agentmail",
+    "email",
+    "inbox",
+    "drafts",
+    "threads",
+    "mcp",
+    "agents"
+  ],
+  "category": "integrations",
+  "tags": [
+    "agentmail",
+    "email",
+    "mcp",
+    "inbox"
+  ],
+  "variables": {
+    "type": "object",
+    "properties": {
+      "AGENTMAIL_API_KEY": {
+        "type": "string",
+        "title": "AgentMail API key",
+        "description": "API key from https://console.agentmail.to under Settings → API Keys. Copy the full value, including the am_ prefix."
+      }
+    },
+    "required": [
+      "AGENTMAIL_API_KEY"
+    ]
+  },
+  "mcpServers": "./mcp.json"
+}

third_party/agentmail/CHANGELOG.md

@@ -0,0 +1,9 @@
+# Changelog
+
+All notable changes to this plugin will be documented here.
+
+## 1.0.0 — initial release
+
+- Logo: AgentMail's official GitHub organization mark.
+- Added the `agentmail` MCP server pointing at `https://mcp.agentmail.to/mcp`.
+- Declared the `AGENTMAIL_API_KEY` plugin variable and forwarded it through the `x-api-key` header, matching AgentMail's documented Cursor API-key path.

third_party/agentmail/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Cursor
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

third_party/agentmail/README.md

@@ -0,0 +1,66 @@
+# AgentMail
+
+Cursor plugin that connects agents to [AgentMail](https://agentmail.to) through AgentMail's official hosted [Model Context Protocol](https://modelcontextprotocol.io/) server.
+
+Give agents their own inboxes: create addresses, send and receive mail, search threads, and manage drafts and attachments.
+
+## Install
+
+1. Open **Cursor Settings → Plugins**.
+2. Search for **AgentMail**.
+3. Click **Install**, then set your AgentMail API key (below).
+
+Or run `/add-plugin agentmail` in chat.
+
+## MCP
+
+```json
+{
+  "mcpServers": {
+    "agentmail": {
+      "type": "http",
+      "url": "https://mcp.agentmail.to/mcp",
+      "headers": {
+        "x-api-key": "${AGENTMAIL_API_KEY}"
+      }
+    }
+  }
+}
+```
+
+## What agents can do
+
+| Category | Capabilities |
+| --- | --- |
+| Inboxes | List, get, create, update, and delete agent inboxes |
+| Threads | List, search, get, update, and delete conversations |
+| Messages | List, search, send, reply, forward, and update messages; fetch attachments |
+| Drafts | Create, list, get, update, send, and delete drafts |
+
+The hosted runtime is the source of truth for tool names and schemas. Call `list_inboxes` as a read-only smoke test after connecting.
+
+## Setup
+
+No credential ships with this plugin — it carries only a `${AGENTMAIL_API_KEY}` placeholder, and each install supplies its own key.
+
+1. Open the [AgentMail console](https://console.agentmail.to).
+2. Go to **Settings → API Keys** and create a key.
+3. Copy the full value, including the `am_` prefix.
+4. In **Dashboard → Plugins → Configure**, set **AgentMail API key** to that value.
+
+Tool calls run with that key's organization, pod, and inbox scope. Rotate or revoke the key from the console if it is ever exposed.
+
+Prefer the `x-api-key` header (what this plugin ships). Query-string keys end up in logs and history. AgentMail also accepts `Authorization: Bearer <am_...>` if a client requires that form.
+
+## Docs
+
+- AgentMail MCP (Cursor API key): https://www.agentmail.to/docs/integrations/mcp#cursor-api-key
+- Hosted server: https://mcp.agentmail.to/mcp
+- Console: https://console.agentmail.to
+- MCP implementation: https://github.com/agentmail-to/agentmail-mcp
+
+Logo is AgentMail's official GitHub organization mark.
+
+## License
+
+MIT

third_party/agentmail/mcp.json

@@ -0,0 +1,11 @@
+{
+  "mcpServers": {
+    "agentmail": {
+      "type": "http",
+      "url": "https://mcp.agentmail.to/mcp",
+      "headers": {
+        "x-api-key": "${AGENTMAIL_API_KEY}"
+      }
+    }
+  }
+}