Custom MCP servers are connected in ChatGPT as "Plugins" (Plugins / Apps in the English interface) and are available only when Developer mode is enabled. Plans: Plus, Pro, Business, Enterprise, Edu (web version).

Authorization uses OAuth 2.1: you add the MCP server URL in ChatGPT's settings → ChatGPT contacts the server without a token and receives an authorization request → the Email Massivo sign-in page opens, you log in to your account and click "Allow" → ChatGPT receives an access token, and the connection is ready to use.

MCP server URL: https://mcp.emailmassivo.com/mcp

Step 0 — enable Developer mode

  1. Open Settings → the "Browser" section (in the "Integrations" group of the left menu) and scroll down to the "Developer mode" block.

  2. The block is marked with an "Elevated risk" badge.

  3. Turn on the "Enable full CDP access" toggle.


Settings → "Browser" → "Developer mode" → "Enable full CDP access" toggle

On Business/Enterprise/Edu plans, the toggle may be unavailable to a regular user — an administrator must first allow it in Workspace Settings → Permissions & Roles → Connected Data.

Steps — adding a plugin (connector)

  1. Open "Plugins" in the left sidebar (the item below "Scheduled"). If the panel is collapsed, expand it first with the icon in the top-left corner. The page has two tabs — "Plugins" and "Skills"; you need the first one.

  2. Click "+" to the right of the "Search plugins" field.


"Plugins" page — "+" button to the right of the search field

  1. In the "New plugin" window that opens, enter Email Massivo in the "Name" field. The "Icon" and "Description" fields are optional (icon — PNG only, at least 256 × 256 px, up to 10 KB).

  2. In the "Connection" block, leave the switch set to "Server URL" (not "Tunnel") and paste: https://mcp.emailmassivo.com/mcp

  3. In the "Authentication" field, select OAuth (not "No authentication"). The "Advanced OAuth settings" section does not need to be expanded — ChatGPT will pull the authorization parameters from the server itself.

  4. Check the "I understand and want to continue" checkbox below the warning about the risks of custom MCP servers.

  5. Click "Create".


"New plugin" window: Name, Server URL, Authentication — OAuth, risk confirmation

  1. Return to the "Plugins" page and switch to the "Personal" tab — the created plugin appears in the "Created by me" block. Click "+" next to it to connect.


"Personal" tab → "Created by me" block: the created Email Massivo plugin

  1. The Email Massivo authorization page opens — log in to your account and click "Allow".


Email Massivo authorization page — "Allow" button

  1. After successful authorization, the plugin becomes active and can be called in the chat.