# How do I connect multiple Gmail accounts to Gemini?

> Gemini CLI takes any remote MCP server in settings.json. The Gemini app needs a Spark custom app, with limits: US, English, personal account. Steps for both.

Updated: 2026-10-03 · Canonical: https://staging.nickbox.io/en/resources/connect-multiple-gmail-accounts-to-gemini

Gemini's built-in Gmail extension is the simplest choice for one inbox. For several, use Gemini CLI if you can: it takes any remote MCP server in `settings.json` with no regional limits we know of. The Gemini app can use one too, through a Spark custom app, but only on personal accounts in the US in English. Nickbox gives either route one URL for up to 5 inboxes.

## Can the Gemini app connect to a custom MCP server?

Yes, through Gemini Spark custom apps, which Google started offering around 2026-06-29. Google's [support page](https://support.google.com/gemini/answer/17209137) lists the limits: a personal Google account, age 18 or older, in the US, in English, on the web, with a Google AI Pro or Ultra plan. [TechRepublic's coverage](https://www.techrepublic.com/article/news-gemini-spark-app-integrations/) matches this.

That rules out a lot of people. If your Gemini account is a Workspace account, or you are outside the US, Spark custom apps are not available to you today. Google may widen the list, so check the support page before you give up.

## How do I add Nickbox as a custom app in the Gemini app?

Open Settings, then Connected Apps, then Custom apps, and choose Add a custom app. Paste your MCP URL and approve the sign-in.

1. Connect your inboxes in Nickbox and give each a nickname (`work`, `personal`, `billing`).
2. Copy your MCP URL from the dashboard.
3. In Gemini on the web, go to Settings, Connected Apps, Custom apps, Add a custom app.
4. Paste the URL, name the app and approve the OAuth sign-in.
5. Ask: "Which of my inboxes can you see?"

The [Gemini guide](/en/docs/gemini) keeps the current screens. Google changes labels in Gemini often.

## How do I connect Gemini CLI to several Gmail accounts?

Add Nickbox to the `mcpServers` section of `~/.gemini/settings.json`, using `httpUrl` for a streamable HTTP server. Gemini CLI discovers the OAuth settings on its own. Then you sign in once and every inbox you connected in Nickbox is available.

1. Connect your inboxes in Nickbox and copy your MCP URL.
2. Open `~/.gemini/settings.json` and add:

```json
{
  "mcpServers": {
    "nickbox": {
      "httpUrl": "https://mcp.example.com/mcp"
    }
  }
}
```

3. Replace the example URL with your own, then start Gemini CLI.
4. Run `/mcp auth` and finish the sign-in in the browser. Gemini CLI keeps the tokens in `~/.gemini/mcp-oauth-tokens.json`.
5. Ask: "Search `work` and `billing` for invoices from September."

The [Gemini CLI documentation](https://github.com/google-gemini/gemini-cli/blob/main/docs/tools/mcp-server.md) covers other fields, and the [Gemini guide](/en/docs/gemini) has our troubleshooting notes.

## What about Gemini Enterprise and Workspace?

Gemini Enterprise has a Custom MCP Server data store, and Google lists it as a Preview that an admin configures. Individual Workspace users cannot add it themselves. If your company uses Workspace, you also need the admin to allow the app that reads Gmail; see [how to ask your Workspace admin to allow an MCP app](/en/resources/allow-mcp-app-in-google-workspace).

Because a Preview can change, we do not describe its steps here. Read [Google's setup page](https://docs.cloud.google.com/gemini/enterprise/docs/connectors/custom-mcp-server/set-up-custom-mcp-server) with your admin.

## How do I check that Gemini sees all my inboxes?

Ask a question that forces a list: "Which accounts do you see?" The assistant calls `list_accounts` and answers with your nicknames. If one is missing, open the Nickbox dashboard and confirm that inbox shows as connected; a Google sign-in that was never finished is the usual cause. Then run a narrow search in each inbox by nickname before you trust a search across all of them.

## Which Gemini route should I pick?

Pick by account type and location. The table shows what each route needs.

| Route | Needs | Good for |
|---|---|---|
| Gemini CLI | A terminal and a remote MCP URL | Developers, no regional limits we know of, personal or Workspace inboxes where the admin allows the app |
| Gemini app, Spark custom app | Personal account, 18+, US, English, web, AI Pro or Ultra | People who live in the Gemini app |
| Gemini Enterprise custom MCP | Admin setup, Preview feature | Companies already on Gemini Enterprise |

If you are not in the US and do not want a terminal, another assistant will serve you better today. Claude and ChatGPT both accept a custom connector; see [Claude](/en/docs/claude) and [ChatGPT](/en/docs/chatgpt). Pricing is on the [pricing page](/en/pricing): US$5 a month or US$48 a year. Nickbox is read-only and stores no message content, per the [security page](/en/security).

## FAQ

**Can the Gemini app use a custom MCP server?**

Yes, through Gemini Spark custom apps, available since late June 2026. It is limited to personal accounts, ages 18 and up, in the US, in English, on the web, with an AI Pro or Ultra plan.

**Does Gemini Spark work with Google Workspace accounts?**

Not according to Google's support page: custom apps are for personal accounts. Workspace users can use Gemini CLI or ask an admin about Gemini Enterprise.

**Where do I put the MCP server in Gemini CLI?**

In the mcpServers object of ~/.gemini/settings.json, using httpUrl for a streamable HTTP server. Then run /mcp auth to sign in.

**Is Gemini Enterprise custom MCP generally available?**

No. Google documents the Custom MCP Server data store as a Preview, and an admin configures it.

## Sources

- [Gemini Apps Help: custom apps in Gemini Spark](https://support.google.com/gemini/answer/17209137)
- [Gemini Spark app integrations (TechRepublic)](https://www.techrepublic.com/article/news-gemini-spark-app-integrations/)
- [Gemini CLI: MCP servers](https://github.com/google-gemini/gemini-cli/blob/main/docs/tools/mcp-server.md)
- [Gemini Enterprise: set up a custom MCP server](https://docs.cloud.google.com/gemini/enterprise/docs/connectors/custom-mcp-server/set-up-custom-mcp-server)