Connect Nickbox to Claude

Add Nickbox once as a custom connector in Claude and every inbox you connect shows up there by its nickname. Claude calls a plug-in a "connector", and Nickbox is a Gmail MCP server that you add as a custom one. It sits next to Claude's own Gmail connector, which reads the one Google account you connected, per Claude's help page (checked 2026-10-03). Compare the two in Gmail connector vs Gmail MCP server.

Before you start

• A Nickbox account with at least one inbox connected in the dashboard.
• Your MCP URL. In this guide it is https://nickbox.io/mcp. The real one is in the dashboard under Connect.
• A Claude plan that allows custom connectors. The Free plan is limited to one custom connector. Pro, Max, Team and Enterprise allow more.

Steps (Pro, Max and Free)

1. In Claude on the web or desktop, open Customize, then Connectors.

2. Click Add, then Add custom connector.

3. Enter the name Nickbox and paste your MCP URL:

   https://nickbox.io/mcp
   

4. Save, then click Connect next to Nickbox.

5. Sign in with Google on the Nickbox screen and approve access. Nickbox asks for read-only Gmail permission.

6. Back in Claude, open a new chat and make sure the Nickbox connector is switched on for it.

Menu names change between Claude versions. If you do not see these exact labels, look for a Connectors page under Customize or Settings.

Steps (Team and Enterprise)

On these plans an organization Owner adds the connector first.

1. The Owner opens Organization settings, then Connectors, and adds a custom connector with the URL above.
2. Each member then opens Customize, then Connectors, finds Nickbox and clicks Connect.

Check it works

Start a new chat and type:

list my inboxes

Claude should call list_accounts and answer with your nicknames, for example work, personal and billing. Then try Search work for invoices from last month.

Troubleshooting

• There is no "Add custom connector" option. Your plan or organization may not allow it. On Team and Enterprise, ask an Owner. On Free you can have only one custom connector, so remove another first.
• Claude says it cannot reach the server. Check that you pasted the full URL ending in /mcp and that it starts with https://. Claude connects from Anthropic's servers, so the URL must be public.
• Google shows "This app is blocked" or "admin_policy_enforced". Your Workspace admin has to allow Nickbox. See the Workspace admin guide.
• Google shows an "unverified app" warning. Nickbox has not finished Google's verification yet, so Google shows that warning and lets the app connect only 100 Gmail accounts. Continue only if you trust the app, and see the beta notes on the site.
• The connector shows but tools are missing. Remove it and add it again, then start a new chat.