Add In-Reply-To to Email Workflow Node (#18641)

Co-authored-by: github-actions <github-actions@twenty.com> Co-authored-by: Charles Bochet <charles@twenty.com>
2026-03-22 21:19:08 +05:30
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+---
+title: Auto-Reply to Inbound Emails
+description: Build a workflow that uses AI to triage incoming emails and send threaded replies automatically.
+---
+
+Respond to inbound emails in seconds — not hours. This workflow uses an AI Agent to filter out noise (newsletters, spam, auto-replies) and draft a personalized response to real messages, then sends it as a threaded reply inside the original conversation.
+
+## How email threading works
+
+Every email carries a hidden `Message-ID` header — a unique fingerprint assigned by the sender's mail server. When you reply to an email, your mail client sets an `In-Reply-To` header referencing that fingerprint. That's how Gmail, Outlook, and every other client groups messages into threads.
+
+In Twenty, that fingerprint is stored as `headerMessageId` on the Message object. Your workflow grabs it and passes it into the Send Email action's In-Reply-To field.
+
+## Building the workflow
+
+### Step 1: Create a new workflow
+
+Head to **Settings -> Workflows** and click **+ New Workflow**.
+
+### Step 2: Trigger on incoming messages
+
+Pick **When a Record is Created** and choose **Messages**.
+
+Every time an email lands in Twenty, this fires.
+
+<img src="/images/user-guide/workflows/auto-reply/workflow-overview.png" style={{width:'100%'}}/>
+
+### Step 3: Look up who sent it
+
+Add a **Search Records** action.
+
+The sender's address isn't on the message itself — it's on the related Message Participant record.
+
+| Field | Value |
+|-------|-------|
+| **Object** | Message Participants |
+| **Filter** | Message **is** `{{trigger.id}}` |
+| **Filter** | Role **is** From |
+| **Limit** | 1 |
+
+This gives you the sender's email in `handle` and their name in `displayName`.
+
+<img src="/images/user-guide/workflows/auto-reply/find-sender.png" style={{width:'100%'}}/>
+
+### Step 4: AI triage and draft reply
+
+Add an **AI Agent** action. This single step does two things: decides whether the email deserves a reply, and if so, writes one.
+
+Use a prompt like:
+
+```
+You are an email triage assistant for a sales team. Read the following
+inbound email and decide if it deserves a reply.
+
+Subject: {{trigger.subject}}
+Body: {{trigger.text}}
+From: {{Find Sender.first.displayName}} ({{Find Sender.first.handle}})
+
+If this email is spam, a newsletter, an automated notification, or
+otherwise does not need a human reply, respond with exactly: SKIP
+
+Otherwise, write a short, professional reply (3-4 sentences max) that:
+- Acknowledges their specific message
+- Lets them know someone from the team will follow up shortly
+- Is warm but not overly casual
+
+Respond with only the reply text, no subject line or greeting prefix.
+```
+
+The AI Agent outputs its response in a `response` field that the next steps can reference.
+
+<img src="/images/user-guide/workflows/auto-reply/ai-triage.png" style={{width:'100%'}}/>
+
+### Step 5: Branch on the AI decision
+
+Add an **If/Else** action to check whether the AI decided to reply or skip.
+
+| Field | Value |
+|-------|-------|
+| **Condition** | AI Agent `response` **does not contain** `SKIP` |
+| **If true** | Continue to Send Email |
+| **Else** | Do nothing (workflow ends) |
+
+Spam, newsletters, and auto-generated messages get dropped. Everything else moves to the next step.
+
+<img src="/images/user-guide/workflows/auto-reply/should-reply.png" style={{width:'100%'}}/>
+
+### Step 6: Send a threaded reply
+
+Add a **Send Email** action on the "if true" branch. Click **Advanced options**, then **Add In-Reply-To**.
+
+| Field | Value |
+|-------|-------|
+| **To** | `{{Find Sender.first.handle}}` |
+| **Subject** | `Re: {{trigger.subject}}` |
+| **Body** | `{{AI Triage & Draft Reply.response}}` |
+| **In-Reply-To** | `{{trigger.headerMessageId}}` |
+
+The In-Reply-To field is what makes this a reply instead of a new conversation. The recipient sees it threaded under the original email in Gmail, Outlook, or any other client.
+
+<img src="/images/user-guide/workflows/auto-reply/send-email.png" style={{width:'100%'}}/>
+
+<Tip>
+**In-Reply-To** expects a `message.headerMessageId` from the trigger — it's the email's unique fingerprint, not a recipient address. If you leave it empty, the email still sends, just as a standalone message.
+</Tip>
+
+<Warning>
+Gmail uses the subject line to group messages into threads. The subject **must** start with `Re:` (including the colon and space) for Gmail to display the reply inside the original thread. Without it, the reply will appear as a separate conversation — even if the In-Reply-To header is set correctly.
+</Warning>
+
+### Step 7: Test and activate
+
+Hit **Test**, then check your email client. The reply should appear nested under the original message.
+
+Activate when you're happy with it.
+
+## Ideas to build on
+
+- **Only reply to VIPs** — add a branch that checks the sender's domain or whether they exist as a Contact in Twenty
+- **Route by intent** — use separate AI Agent prompts to handle sales inquiries differently from support requests
+- **Enrich before replying** — add a Search Records step to pull the sender's company or deal history into the AI prompt for more personalized replies