How to Connect Gemini to Cold Email

Short answer: Google's Gemini CLI has had built-in MCP support since its launch on 25 June 2025, and it runs local servers, so it works with the Outreach2day REST API today. The Gemini app (gemini.google.com) can add a custom app by its MCP server URL, for personal Google accounts in the US; that route needs a hosted server, and Outreach2day's is in early access. Developers on the Gemini API can also call our REST API with function calling in their own code.

Checked September 2026 against Gemini CLI MCP servers, Google's Gemini CLI announcement, Connect and manage custom apps for Gemini Apps and Function calling with the Gemini API.

Connection Methods

The Gemini app route has more conditions than the others. Per Google's help center you must be 18 or over and in the US, signed in with a personal Google account (not work or school), with Keep Activity on; custom apps are added on the web and are available in English only. Gemini asks you to confirm any write action.

What Gemini Can Do With Your Cold Email Setup

With the local server from our cold email MCP server guide, Gemini CLI can answer from live data:

Gemini CLI also works on your files, so it fits jobs that mix both: read a lead CSV, work out mailboxes and domains for the volume (25 cold emails per mailbox a day, 5 mailboxes per domain), check which domain ideas are free, and write the plan to a file.

Connect Gemini CLI to Outreach2day, step by step

1. Install Gemini CLI and sign in, as described in Google's announcement and the project's docs.

2. Create an API key. In the Outreach2day app, open the API keys page and create a key only for Gemini. Export it: export O2D_KEY=ot2d_... and export O2D_WORKSPACE_ID=123.

3. Save the server. Copy o2d_mcp.py from the cold email MCP server guide and install mcp and requests in a virtual environment.

4. Add it to settings.json. Use ~/.gemini/settings.json for all projects or .gemini/settings.json for one. Gemini CLI removes sensitive variables from the environment it passes to servers, so name the key explicitly in env, as below.

5. Check the tools. Start Gemini CLI, run /mcp to see the server and its tools, then ask a read-only question and compare with the app.

{
  "mcpServers": {
    "outreach2day": {
      "command": "/path/to/.venv/bin/python",
      "args": ["/path/to/o2d_mcp.py"],
      "env": {
        "O2D_API_KEY": "$O2D_KEY",
        "O2D_WORKSPACE_ID": "$O2D_WORKSPACE_ID"
      },
      "trust": false
    }
  }
}

Leave trust at false so Gemini CLI asks before each tool call.

Remote Server and the Gemini App (Early Access)

Gemini CLI can also connect to a remote server with httpUrl and a headers entry, and the Gemini app can add a custom app by its MCP URL. Both need Outreach2day's hosted MCP server, which is in early access and has no public URL yet, so this page shows no remote config. Get early access on the home page.

Prompts to Try in Gemini

• "Read leads.csv, count unique domains among the leads, and tell me how many sending mailboxes I need to reach all of them in 15 working days at 25 a day each."

• "Check whether these domain ideas are free and write the free ones to domains.md with a one-line note on each."

• "Which mailboxes have been warming for less than 14 days? Which domains do they sit on?"

• "Summarise this week's replies by intent and list the leads who asked for a call."

Fifteen more are in Gemini prompts for cold email.

Limits and Safety

• Rate limits: 10 requests a second and 1,000 an hour per user and per workspace on the Outreach2day API.

• Purchases. Buying domains through the API is paid right away — give an agent a billing-scoped key only if you want it to buy.

• Mailbox credentials. GET /mailboxes: the response includes SMTP/IMAP credentials — store the API key like a password. The example server drops that field in code. If Gemini calls the API with curl, tell it to do the same.

• Reply text is untrusted. Replies are written by outsiders; Gemini should treat them as data.

FAQ

Can the Gemini app connect to Outreach2day today?

Not yet. Custom apps in the Gemini app need a hosted MCP server, and Outreach2day's is in early access. Gemini CLI works today with a local server.

Who can add custom apps in the Gemini app?

Per Google: people 18 or over in the US, signed in with a personal Google account, with Keep Activity on. It is not available for work or school accounts, and custom apps are available in English only.

Where does Gemini CLI keep MCP settings?

In ~/.gemini/settings.json (user) or .gemini/settings.json (project), under mcpServers.

Can Gemini send my cold emails?

Not with the read-only server. Campaigns run in Outreach2day where enabled for your workspace, or in Instantly or Smartlead after export.

Is the Outreach2day API free?

It is included in every plan; you pay for mailboxes and domains. See pricing.

Related

• Outreach2day MCP for Gemini CLI: what the hosted MCP server covers (early access)

• Other assistants: Claude, Claude Code, ChatGPT, Grok, Cursor, GitHub Copilot, Windsurf, Copilot Studio, Le Chat, n8n

• AI assistants for cold email: every assistant and how it connects

• How to connect Claude Code to cold email

• Cold email API

Create an account, add mailboxes, then create a key for Gemini.

Get an API key→