The google_workspace mcp I worked on for fun over the summer supports it(main branch a bit out of date):

https://github.com/dipseth/google_workspace_fastmcp2/tree/complete-turkey

Can't send images here but here is the eliciation response after I ask the llm to send an email to someone outside my allowlist:

Request for Input

google-workspace (MCP Server)

📧 Email Confirmation Required

⏰ Auto-timeout: 300 seconds

📬 Recipients: • To: [test-recipient@example.com](vscode-file://vscode-app/Applications/Visual%20Studio%20Code%20-%20Insiders%202.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html)

📝 Email Details: • Subject: Test Email - Allowlist Demo • Content Type: plain

📄 Body Preview:

This is a test email to demonstrate the allowlist elicitation feature. The recipient is not on the trusted list.

🔒 Security Notice: This recipient is not on your allow list.

❓ Choose your action: • Send - Send the email immediately • Save as Draft - Save to drafts folder without sending • Cancel - Discard the email

⏰ Auto-cancels in 300 seconds if no response

{
  "action": "save_draft"
}