Verify & Update Mailing Addresses in Groundhogg CRM with n8n

Opening Problem Statement

Meet Jane, a small business marketer who manages customer relationships using Groundhogg CRM. Jane often spends hours manually checking if the mailing addresses entered into the CRM are accurate and deliverable. Misspellings or incomplete addresses frequently lead to returned mail, hindering her marketing campaigns and customer outreach—resulting in wasted postage, lost time, and frustrated customers.

Imagine Jane receiving hundreds of new contacts weekly, each needing a quick and reliable verification process. Without automation, she risks errors, delays, and unnecessary manual work. This exact challenge is solved by the n8n workflow we’re about to explore.

What This Automation Does

This custom-built n8n workflow automatically verifies mailing addresses for new contacts added to Groundhogg CRM. When a new contact is created, the workflow:

• Receives a webhook from Groundhogg CRM with the contact’s address details.
• Extracts and formats the address fields.
• Uses the Lob API to verify if the address is deliverable in the US.
• Tags the contact in Groundhogg CRM as “Mailing Address Deliverable” if valid.
• Tags the contact as “Mailing Address NOT Deliverable” if the address is invalid, triggering follow-up workflows.
• Helps catch misspellings and incorrect addresses automatically, reducing manual corrections.

Overall, this saves Jane hours of manual checking each week and improves mail campaign success rates significantly.

Prerequisites ⚙️

• n8n account to build and run the workflow
• Groundhogg CRM with webhook capability enabled to send contact data
• Lob.com account to use their US address verification API
• API Key from Lob for authentication (Basic Auth used in HTTP Request node)
• HTTP Request node access in n8n (comes by default)
• Webhook node access in n8n (to receive CRM data)

Step-by-Step Guide to Build & Deploy the Workflow

1. Set Up Webhook to Receive Contact Data from Groundhogg CRM

In n8n, add a Webhook node and configure it:

• Navigate to Nodes Panel → Webhook
• Set the HTTP method to POST
• Create a unique webhook path, for example: 727deb6f-9d10-4492-92e6-38f3292510b0
• Save and activate the webhook to get its URL
• In Groundhogg CRM, configure a webhook to send new contact details to this URL upon new contact creation

After setup, you can test this webhook sending via Groundhogg or by using a REST client. Incoming data should look like the example in the workflow: contact ID, address, state, city, and zip.

2. Extract and Format Address Fields with the Set Node

Add a Set node connected to the Webhook node:

• Assign variables for address fields: address, address2 (empty), city, state, and zip
• Use expressions to map data from the webhook JSON, for example: {{$json.address}}, {{$json.city}}, {{$json.state}}, {{$json.zip_code}}

This organizes the data for the Lob API request.

Common Mistake: Not including all required address fields can cause API errors.

3. Verify the Address Using Lob API with HTTP Request Node

Add an HTTP Request node configured as follows:

• URL: https://api.lob.com/v1/us_verifications
• Method: POST
• Authentication: Set to Basic Auth using your Lob API key
• Body Parameters: Map the address fields from the previous Set node

Example body parameters:

{
  "primary_line": "1600 Pennsylvania Avenue NW",
  "secondary_line": "",
  "city": "Washington",
  "state": "DC",
  "zip_code": "20500"
}

On execution, this node sends the address to Lob and receives delivery status.

4. Add a Switch Node to Check Deliverability Status

Add a Switch node connected to the HTTP request:

• Use expression {{$json.deliverability}} as value to test
• Rule 1: If equals “deliverable” → Route to Deliverable actions
• Rule 2: If not equals “deliverable” → Route to Non-deliverable actions

This node directs flow based on address validation.

5. Tag Deliverable Addresses in Groundhogg CRM

Add an HTTP Request node for tagging deliverable contacts:

• Set method to POST
• URL is the Groundhogg webhook listener URL that handles tag update
• Set body parameters to include:
• tag = "Mailing Address Deliverable"
• id = {{ $('CRM Webhook Trigger').item.json.id }}

This automatically adds a tag in Groundhogg CRM for valid addresses.

6. Tag Non-Deliverable Addresses & Trigger Manual Follow-Up

Add a second HTTP Request node for non-deliverable addresses:

• Configure similar to the deliverable node but with tag: Mailing Address NOT Deliverable
• This tag can trigger a separate workflow for manual verification or customer outreach

Common Mistake: Incorrect URL or missing contact ID causes tagging failures.

7. Finalize & Activate Workflow

Test your workflow by submitting contact data. Check Groundhogg CRM that tags update appropriately.

Once confirmed, activate the workflow in n8n to run automatically whenever a new contact is added.

Customizations ✏️

• Trigger alternative actions: In the “Update Groundhogg – NOT Deliverable” node, change the tag action to start an automation that emails the contact for address verification.
• Add a note in Groundhogg: Use an HTTP Request to add detailed address verification notes instead of tags.
• Support international addresses: Integrate an additional API to handle non-US addresses by adding decision nodes before Lob API call.
• Include address correction suggestions: Parse Lob API response and update CRM fields with corrected address components automatically.
• Use multiple Lob API keys: Rotate or use different keys based on volume or environment by updating HTTP Request authentication.

Troubleshooting 🔧

Problem: “HTTP 401 Unauthorized” response from Lob API

Cause: Incorrect or missing API key in Basic Auth headers.

Solution: Double-check Lob API key, re-enter it in the HTTP Request node’s credentials section, and test the node again.

Problem: “Webhook not receiving data from Groundhogg CRM”

Cause: Webhook URL is incorrect or Groundhogg is not configured to send webhooks.

Solution: Confirm webhook URL copied from n8n matches the CRM configuration. Check CRM webhook logs or test sending sample data manually.

Problem: “Tag update not reflected in Groundhogg”

Cause: Incorrect endpoint URL or missing contact ID in the HTTP Request node.

Solution: Verify the POST URL and ensure the ID parameter matches the latest webhook data. Use debug mode in n8n to trace data.

Pre-Production Checklist ✅

• Ensure your Lob API key is valid and has sufficient quota
• Confirm Groundhogg webhook is active and correctly sending contact data
• Test webhook reception in n8n using sample contact data
• Validate HTTP Request node responses for both deliverable and non-deliverable routes
• Check tags are correctly added or updated in Groundhogg CRM
• Create a backup of your workflow JSON for rollback if needed

Deployment Guide

After thorough testing, activate your n8n workflow by toggling it from inactive to active so it listens for every new webhook event from Groundhogg CRM. Monitor workflow executions through the n8n dashboard to catch and fix any errors early.

For production environments, consider hosting n8n on a reliable cloud server (self-hosted options available at Hostinger) for better uptime and control.

FAQs

Can I use a different address verification API other than Lob?

Yes, you can replace the HTTP Request node calling Lob with another API, but you will need to adjust authentication, parameters, and response parsing accordingly.

Does this workflow consume API credits or cost money?

Lob’s API has usage limits and pricing tiers. Ensure you review Lob’s pricing to understand costs and monitor usage to avoid unexpected charges.

Is my contact data secure with this workflow?

All data processing happens within your n8n instance, and webhooks use HTTPS endpoints. Secure your API keys and n8n access with best practices to keep data safe.

Can this workflow handle bulk contact imports?

It is designed for real-time verification on single contact creation via webhooks. For bulk, you may need to batch process addresses with custom scripting or separate workflows.

Conclusion

By following this guide, you’ve created an efficient n8n workflow that verifies and tags mailing addresses for new Groundhogg CRM contacts automatically. This automation saves valuable time, reduces errors and postage losses, and improves your customer mailing accuracy.

As a next step, consider enhancing this workflow to handle international addresses or automate notifications to contacts for verification. You could also integrate with mailing services to print verified address labels directly.

Keep experimenting and automating—your time is precious, and with tools like n8n and Lob, you can focus more on growing your business and less on manual data cleanup.