Connect Gemini to Postal

Check these points before opening the Gemini setup. They prevent most connection failures.

• A team with the "MCP server" plan feature (mcp_access); without it the server responds 403 plan_limit_reached.
• To send emails, the team needs at least one verified domain.
• If you will use an API key: create the key in the dashboard, under API keys. It starts with ps_; a send-only key is enough if you will only send.
• Each connection acts on a single team. To use another team, connect again and pick the other one.
• Connections are listed under Settings › AI connections in the dashboard, where they can be revoked at any time.

Follow the steps in order. The server address is always https://api.postal.so/mcp. Recommended path: sign in with your account (OAuth). The API key is the alternative. Wherever ps_... appears, use your own API key: the value shown is only an example.

1. 1

   Gemini CLI: run the first command (it creates the entry in the project's .gemini/settings.json; to apply to all projects, edit ~/.gemini/settings.json with the second snippet).

2. 2

   Inside the Gemini CLI, run /mcp auth postal. The browser opens the Postal login; choose the team and click Allow. The login needs a local browser (it does not work over SSH without X11 or in a container without a browser).

3. 3

   For an API key, use the third command.

4. 4

   Antigravity (Google): edit ~/.gemini/config/mcp_config.json with the fourth snippet (the field is serverUrl; url and httpUrl do not work there). Under Agent settings > Customizations, click Authenticate, finish the login and paste the authorization code into the panel.

gemini mcp add --transport http postal https://api.postal.so/mcp

{
  "mcpServers": {
    "postal": {
      "httpUrl": "https://api.postal.so/mcp"
    }
  }
}

gemini mcp add --transport http --header "Authorization: Bearer ps_..." postal https://api.postal.so/mcp

{
  "mcpServers": {
    "postal": {
      "serverUrl": "https://api.postal.so/mcp"
    }
  }
}

Postal splits access into three levels, explained in the scopes table. For Gemini:

The simplest proof is to ask for something read-only inside Gemini itself. The connection also shows up under Settings › AI connections in the Postal dashboard, with the app, the team and the last use.

For those who want the technical proof

npx @modelcontextprotocol/inspector --cli https://api.postal.so/mcp \
  --transport http \
  --header "Authorization: Bearer ps_..." \
  --method tools/list

The Inspector proves that the Postal server responds. It does not test Gemini itself. The full walkthrough is in Validate the connection.

Go through the list in order. Then read what we know (and what we don't know) about Gemini.

What was tested and what was not