Validate HighLevel Contact Addresses Automatically with n8n and Lob API

Opening Problem Statement

Meet Sarah, the operations manager of a growing real estate consultancy. Every week, Sarah imports dozens of new client contacts into HighLevel CRM, manually entering their mailing addresses to send out important contracts and welcome kits. But problems arise frequently — addresses are misspelled, incomplete, or invalid, causing packages to return undelivered, damaging client relationships and wasting precious staff hours on corrections.

Sarah estimates that manually verifying these addresses takes her team at least 4 hours per week, plus countless follow-up calls for corrections. A single undeliverable mail costs both time and money — lost postage fees, delayed client onboarding, and dissatisfaction. Sarah desperately needs a reliable way to automate validation and ensure mailing accuracy directly from HighLevel.

What This Automation Does

This precise n8n workflow connects HighLevel with Lob’s Address Verification API, giving Sarah and anyone else a seamless way to automatically verify mailing addresses for new contacts. Here’s what happens when it runs:

• Receives a webhook from HighLevel when a new contact is added, containing mailing address data.
• Extracts and formats necessary address components into a structured form using the Set node.
• Sends the address data to Lob’s US Address Verification API via HTTP Request to check deliverability and identify typos.
• Uses a Switch node to branch the workflow based on whether the address is deliverable or not.
• Automatically updates HighLevel by tagging the contact with either “Mailing Address Deliverable” or “Mailing Address NOT Deliverable.”
• This tagging can trigger further automations — for deliverable addresses, it confirms verification; for non-deliverable ones, it alerts Sarah’s team to review or reach out to the contact.

In total, this saves Sarah at least 4 hours a week she would otherwise spend on manual verification, reduces mailing errors drastically, and enables proactive client outreach.

Prerequisites ⚙️

• n8n account — required to create and run the workflow.
• HighLevel account with API access and the ability to send webhook data when new contacts are created.
• Lob.com account — create an API key under your account at https://lob.com/account-management/api-keys (Basic Auth credentials used in workflow).
• Basic knowledge of how to work with webhook URLs and n8n node configuration.

Step-by-Step Guide

1. Setting Up the CRM Webhook Trigger Node

Navigate to n8n Dashboard → Click New Workflow. Add the Webhook node from the nodes panel.

Configure the webhook node: set method to POST, define a unique path (e.g., 727deb6f-9d10-4492-92e6-38f3292510b0), and activate the webhook URL in your CRM system to send contact data every time a new contact is added.

You should see a webhook URL generated by n8n, which you can use in HighLevel to POST new contact addresses.

Outcome: This node listens for incoming contact data and triggers the workflow.

Common Mistake: Forgetting to set method to POST or not activating the webhook in HighLevel.

2. Mapping Address Fields with Set Node

Add a Set node and connect it to the Webhook Trigger. Here, map the received JSON fields for address components:

• address => {{ $json.address }}
• address2 => “” (blank)
• city => {{ $json.city }}
• state => {{ $json.state }}
• zip => {{ $json.zip_code }}

This standardizes the address data before sending it for verification.

Outcome: Fields are prepared and normalized for the Lob API call.

Common Mistake: Incorrectly referencing JSON data, causing empty or wrong fields.

3. Configuring the HTTP Request Node for Address Verification

Add an HTTP Request node connected to Set node to call Lob’s US Address Verification API.

Set method to POST; URL: https://api.lob.com/v1/us_verifications.

Under body parameters, set the parameters as:

• primary_line = {{ $json.address }}
• secondary_line = {{ $json.address2 }}
• city = {{ $json.city }}
• state = {{ $json.state }}
• zip_code = {{ $json.zip_code }}

Use Basic Auth credentials from your Lob API key.

Outcome: The API returns the deliverability status and any suggested corrections.

Common Mistake: Missing or incorrect API key causing authentication errors.

4. Implementing the Switch Node to Handle Deliverability

Add a Switch node connected to the HTTP Request node to branch processing.

Configure rules to check if $json.deliverability equals “deliverable” or not.

This decides the workflow path: one for deliverable addresses, the other for non-deliverable.

Outcome: Logical routing based on verification results.

Common Mistake: Typo in rule values causing all addresses to route incorrectly.

5. Updating HighLevel for Deliverable Addresses

Connect one output of the Switch node to a HighLevel node and configure it to add the tag “Mailing Address Deliverable” for the contact.

Use the email and phone from the webhook data to identify the contact.

Outcome: Contacts with verified addresses get tagged, confirming deliverability.

Common Mistake: Not mapping identifying fields correctly, leading to update failures.

6. Updating HighLevel for Non-Deliverable Addresses

Connect the other output of Switch to another HighLevel node configured to tag “Mailing Address NOT Deliverable.”

This tag can trigger further manual review workflows in HighLevel.

Outcome: Contacts with problematic addresses get tagged for manual follow-up.

Common Mistake: Forgetting to enable API permissions or tag creation in HighLevel.

Customizations ✏️

• Change Tag Names: In each HighLevel node, edit the “tags” field to reflect your company’s preferred terminology, e.g., “Address Verified” or “Needs Correction.”
• Trigger Email Notification: Add an Email node after the “NOT Deliverable” path to notify your team automatically.
• Extend to International Addresses: Integrate additional APIs or use Lob’s international verification endpoint if needed.
• Enhance Address Data: Use a Code node before the HTTP Request to concatenate secondary address elements or validate data format further.

Troubleshooting 🔧

• Problem: “Authentication Failed” on HTTP Request node.
  Cause: Incorrect API key or Basic Auth setup.
  Solution: Recheck your Lob API key, re-enter credentials under node settings, and test connectivity.
• Problem: Webhook not triggering on new contacts.
  Cause: Webhook URL not configured or activated in HighLevel.
  Solution: Verify webhook URL is correct, method set to POST, and activated in CRM settings.
• Problem: Switch node misrouting all outputs.
  Cause: Typo in deliverability field value or mismatched case.
  Solution: Double-check expected values exactly (“deliverable”) and adjust rules or capitalization.

Pre-Production Checklist ✅

• Confirm Lob API key is active with necessary permissions.
• Test webhook trigger by sending sample contact data with valid and invalid addresses.
• Verify Set node mappings match actual JSON structure of webhook payload.
• Ensure Switch node rules match API response deliverability values exactly.
• Test HighLevel nodes by checking contacts get tagged correctly in the CRM.
• Backup your workflow before major changes for rollback safety.

Deployment Guide

Once tested, activate your workflow in n8n by clicking the Activate toggle in the top right corner.

Monitor the workflow via n8n’s execution logs to troubleshoot any real-time errors or unexpected behavior.

You can optionally configure alert nodes or logging for long-term monitoring if needed.

FAQs

• Can I use a different address verification API? Yes. Replace the HTTP Request node with the API details of your preferred service, ensuring the input/output mappings stay consistent.
• Does this consume API credits? Yes, Lob charges per API call. Monitor usage in your Lob dashboard to avoid unexpected costs.
• Is my data safe? Yes. Using Basic Auth over HTTPS encrypts data transit. Keep your API keys secure.
• Can this handle large volumes? Yes, but monitor n8n plan limits and Lob API quotas as needed.

Conclusion

By following this detailed guide, you’ve built a robust automation to verify new HighLevel contact mailing addresses seamlessly. This workflow drastically reduces the manual effort Sarah once faced, cuts down costly mailing errors, and streamlines client onboarding with verified addresses.

You’re now saving at least several hours weekly and improving your delivery success rates. Next, consider automating follow-up emails for non-deliverable addresses, integrating SMS notifications for address confirmation, or expanding verification to international contacts.

Keep refining and scaling your automations to save even more time and enhance client satisfaction!