How to Automate Gmail to Slack Notifications with n8n

1 Poll Gmail every minute with the Gmail Trigger

The workflow starts with the Gmail Trigger node. It polls the Gmail API on the schedule you pick and emits one n8n item for every new message that matches your filters. Polling every minute is the fastest cadence the trigger offers, which is what makes this n8n workflow feel real time.

Add a Gmail Trigger node and configure:

Node: Gmail Trigger
Poll Times: Every Minute
Event: Message Received
Simplify: Off
Filters:
  Label Names or IDs: INBOX
  Read Status: Unread
  Search: -label:notified
Credential: Gmail OAuth2 API

The Search filter uses normal Gmail search syntax. Excluding the notified label here is the first of two defenses against duplicate Slack posts; the second is the labeling step at the end of the workflow. Turn Simplify off so n8n returns the full message with labelIds, threadId and the parsed from object.

{
  "id": "18c2f4a9d3b7e601",
  "threadId": "18c2f4a9d3b7e601",
  "labelIds": ["INBOX", "UNREAD", "Label_4821907"],
  "snippet": "Hi team, attached is the revised statement of work",
  "subject": "Revised SOW for Q4 rollout",
  "from": { "text": "Dana Ortiz <dana@acmecorp.com>",
            "value": [{ "address": "dana@acmecorp.com", "name": "Dana Ortiz" }] }
}

Custom Gmail labels appear as IDs such as Label_4821907, not as names. You will map those IDs to routes in the Code node, so copy them from the n8n Gmail node's label dropdown or from the Gmail API label list.

2 Store the VIP sender list in a Set node

VIP detection needs a list of addresses that always get the urgent channel. The simplest option is a Set node placed right after the trigger that holds the list as a field. A Google Sheets lookup works the same way if the list changes often, and is covered in the notes below.

Add a Set node named VIP List and configure:

Node: Set (Edit Fields)
Mode: Manual Mapping
Include Other Input Fields: On
Fields to Set:
  Name: vip
  Type: Array
  Value: ["ceo@bigclient.com","dana@acmecorp.com","legal@partnerfirm.io"]

Because Include Other Input Fields is on, the Gmail message passes through untouched and gains a vip array. If you prefer Google Sheets, replace this node with a Google Sheets node using Operation: Get Row(s) on a sheet with one address per row, then collect the column into an array inside the n8n Code node.

{
  "id": "18c2f4a9d3b7e601",
  "subject": "Revised SOW for Q4 rollout",
  "vip": ["ceo@bigclient.com", "dana@acmecorp.com", "legal@partnerfirm.io"]
}

Keep addresses lower case. The Code node lower cases the sender before comparing, so a mixed case entry in the list would never match. Test the node with Execute Step so you can see the n8n output before moving on.

3 Extract the sender and build the Gmail deep link in a Code node

Next, a Code node reduces the raw Gmail payload to the handful of fields Slack needs, decides whether the sender is a VIP, picks a route, and builds a direct link to the message. Running the node in Run Once for Each Item mode keeps the logic simple. Name it Extract Sender and Route, because a later n8n expression refers to it by that name; the n8n Code node runs in a sandbox, so no extra packages are needed.

Node: Code
Language: JavaScript
Mode: Run Once for Each Item

const labelMap = {
  Label_4821907: 'clients',
  Label_4821908: 'billing',
  Label_4821909: 'support'
};
const sender = ($json.from.value[0].address || '').toLowerCase();
const isVip = $json.vip.map(v => v.toLowerCase()).includes(sender);
const hit = ($json.labelIds || []).find(id => labelMap[id]);
let route = hit ? labelMap[hit] : 'support';
if (isVip) route = 'vip';
return {
  json: {
    messageId: $json.id,
    sender,
    senderName: $json.from.value[0].name || sender,
    subject: $json.subject || '(no subject)',
    snippet: ($json.snippet || '').slice(0, 140),
    route,
    isVip,
    gmailLink: 'https://mail.google.com/mail/u/0/#inbox/' + $json.threadId
  }
};

The VIP check runs last on purpose. A message from a VIP that also carries the clients label should go to the urgent channel, not the clients channel, so the VIP assignment overwrites the label route.

{
  "messageId": "18c2f4a9d3b7e601",
  "sender": "dana@acmecorp.com",
  "senderName": "Dana Ortiz",
  "subject": "Revised SOW for Q4 rollout",
  "snippet": "Hi team, attached is the revised statement of work",
  "route": "vip",
  "isVip": true,
  "gmailLink": "https://mail.google.com/mail/u/0/#inbox/18c2f4a9d3b7e601"
}

The deep link uses the thread ID because Gmail opens threads, not single messages. The u/0 segment assumes the first signed in Google account; change it to u/1 if your team uses a second account. n8n does not rewrite the URL for you.

4 Route by label with a Switch node

The n8n Switch node reads the route field and sends each item down exactly one of four outputs. This is where label based channel routing happens, and it is the main difference between this n8n workflow and a batch digest.

Node: Switch
Mode: Rules
Data Type: String
Value 1: {{ $json.route }}
Routing Rules:
  Output 0: Equal to  clients
  Output 1: Equal to  billing
  Output 2: Equal to  support
  Output 3: Equal to  vip
Options > Fallback Output: Extra Output

Rename each output so the canvas stays readable: slack-clients, slack-finance, slack-support and slack-urgent. The Fallback Output catches anything that slips through, for example a route value added to the Code node but not yet to the Switch.

{
  "route": "billing",
  "matchedOutput": 1,
  "outputName": "slack-finance"
}

If you add a fifth label later, add the map entry in the Code node and a fifth rule here. Nothing else in the n8n workflow changes, and the Switch node keeps its own execution data for debugging.

5 Post to the mapped Slack channel

Each Switch output connects to its own Slack node, all configured the same way except for the channel. Using four nodes instead of one expression driven node keeps the channel visible on the n8n canvas and lets you give the urgent channel a different message style.

Add an n8n Slack node to the first output and configure:

Node: Slack
Resource: Message
Operation: Send
Send Message To: Channel
Channel: slack-clients
Message Type: Simple Text Message
Text: *{{ $json.senderName }}* ({{ $json.sender }})
Subject: {{ $json.subject }}
> {{ $json.snippet }}
<{{ $json.gmailLink }}|Open in Gmail>
Options > Include Link to Workflow: Off

For the urgent output, prefix the text with URGENT VIP:. Slack renders <url|label> as a clickable link, which is how the Gmail deep link becomes a one click action. Link the Slack credential once in n8n and reuse it on all four nodes.

{
  "ok": true,
  "channel": "C07URGENT01",
  "ts": "1730736012.004200",
  "message": { "text": "*Dana Ortiz* (dana@acmecorp.com) ..." }
}

Subjects and snippets can contain ampersands or angle brackets, which Slack treats as control characters. If you see broken formatting, escape them in the n8n Code node before building the message text.

6 Add the notified label to prevent duplicates

After Slack succeeds, an n8n Gmail node tags the original message with a notified label. Connect all four Slack outputs to this one node; only one branch runs per item, so the label is added once.

Node: Gmail
Resource: Message
Operation: Add Label
Message ID: {{ $('Extract Sender and Route').item.json.messageId }}
Label Names or IDs: notified

Create the notified label in Gmail before running the n8n workflow. The expression pulls the ID from the Code node by name because the Slack node output replaces $json with its own response. This label, combined with the -label:notified search in step 1, means a message is processed one time even if the workflow restarts or the poll window overlaps.

{
  "id": "18c2f4a9d3b7e601",
  "threadId": "18c2f4a9d3b7e601",
  "labelIds": ["INBOX", "UNREAD", "Label_4821907", "Label_5000112"]
}

7 Test with real messages and activate

Click Execute Workflow and send yourself four test emails, one for each label plus one from a VIP address. Confirm each lands in the right Slack channel, that the Gmail link opens the thread, and that the notified label appears in Gmail. Then toggle the workflow to Active so n8n begins polling every minute.

Watch the first hour of executions in the n8n execution list, and open any failed n8n run to see which node stopped. A healthy run shows one item per new message and no repeated message IDs.