Human-Approved AI Follow-Up Emails

HubSpot + Slack approval flow where AI drafts and a person decides

What it does

A human-in-the-loop automation that drafts follow-up emails for HubSpot contacts with Claude and requires a person to approve or reject each one in Slack before anything happens. Nothing is ever sent automatically: approval only records who decided and when, and creates a HubSpot task for a human to send the email. Built as a demo project on a HubSpot developer test account with fake data only (not client work).

Demo walkthrough

Stack

n8nHubSpotSlack (Block Kit)Claude (Anthropic)Webhooks

IndustrySales, CRM & Lead Automation

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What we built

Draft & Send for Approval

A webhook call with a contact id triggers an n8n workflow that fetches the contact from HubSpot.
Claude drafts a short, polite follow-up from the contact's name and company.
The draft is saved on the HubSpot contact with a Pending status and posted to Slack with Approve and Reject buttons.

Decision Handling & Audit Trail

Clicking a button updates the Slack message to show who decided and when, and removes the buttons.
HubSpot stores the status, approver name and email, and decision time on the contact.
If approved, HubSpot gets a task, 'Send approved follow-up', so a human sends the email.

Safety Design

No auto-send: the flow has no email-sending step.
Every Slack click is verified against the signing secret, and requests older than 5 minutes are rejected.
The webhook answers Slack within its 3-second limit, then does the slow work after.
One decision per draft: repeat or simultaneous clicks are settled with a claim, wait and confirm step.

Testing

Tested approve, reject, repeat clicks, forged signatures, replayed requests, clicks after 6 minutes, and a second approver.
Three simultaneous clicks first created a duplicate task; fixed so exactly one decision and one task are recorded.

Impact

Keeps a person in control of every AI-written email while removing the manual drafting work.
Records who approved or rejected each draft, and when, directly on the HubSpot contact.
Verified safe under forged, replayed and simultaneous requests.
Documented the changes needed for a client rollout: approver lists, secret storage, an explicit send step, edit-before-approve, alerts and data retention.