Automate Email List Building with n8n & Hunter io

Opening Problem Statement

Meet Lucy, a small business owner running a growing online newsletter offering AI productivity tips. Every day, Lucy receives dozens of email sign-ups through her website form. However, she spends hours manually sorting valid emails from typos and fake addresses. This tedious task not only wastes her precious time but also risks her email campaigns being flagged for poor quality lists, which can cost her potential customers and marketing credibility. Lucy wishes there was an easy way to automate validating those emails and adding only the valid ones to her mailing list automatically.

This is exactly where our n8n workflow for automatic email validation and submission comes to the rescue. It’s designed specifically for scenarios like Lucy’s, where you want a hands-free, reliable solution to keep your email list clean and active.

What This Automation Does

Here’s what happens every time someone submits an email through your form using this workflow:

• Immediately receive the form submission via n8n’s built-in Form Trigger node.
• Verify the email address authenticity using the Hunter io Email Verifier node, filtering out invalid emails.
• Automatically check validation status with the If node to decide next steps.
• Only add valid emails to your SendGrid mailing list automatically — no manual sorting needed.
• Ignore invalid emails gracefully using the No Operation (NoOp) node to end the flow silently without errors.
• Keep your email lists clean and free from fake or incorrect addresses, improving delivery rates and campaign effectiveness.

This workflow can save you multiple hours weekly by eliminating manual email checks, reduce bounce rates in your campaigns, and make your email marketing efforts more targeted and efficient.

Prerequisites ⚙️

• n8n account (self-hosting recommended for full control; see Hostinger guide)
• Hunter io account with API key (50 free email verification credits monthly)
• SendGrid account for managing contacts and mailing lists
• Basic knowledge of n8n workflow editor

Step-by-Step Guide to Build and Use This Workflow

Step 1: Create the Form Trigger Node

In your n8n editor, click + Add Node, choose Form Trigger.

Configure the form as follows:

• Set Form Title to “Join my mailing list now”
• Add a form field with label “Email” and mark it as required
• Fill the description with “10x your productivity with my A.I. tips. I’ll cut the B.S. and give you the most practical tips for A.I. automation.”

This form will capture email addresses submitted by visitors. You should see a webhook URL n8n provides; this is where the form data posts to trigger the workflow.

Common mistake: Forgetting to mark the email field as required, which can cause empty submissions.

Step 2: Add the Hunter oauth Email Verifier Node

Click to add a new node and select Hunter from the nodes list.

Set the operation to emailVerifier and map the email parameter to reference the submitted email from the form: {{ $json.Email }}.

Make sure you have added your Hunter API key in credentials and connected it to this node.

This node calls Hunter’s API to confirm if the email is valid.

Common mistake: Not providing the Hunter API credentials correctly, resulting in authorization errors.

Step 3: Configure the If Node to Check Email Validity

Add an If node. In the conditions, match the $json.status field to equal valid.

This node branches your workflow based on whether Hunter verified the email as valid.

Tip: Use exact lowercase “valid” for the check, or the logic may fail.

Step 4: Set Up Adding Valid Contact to SendGrid

Add a SendGrid node.

Configure it to add a contact resource and map the email field to {{ $json.Email }}.

Select your mailing list’s list ID to automatically assign the new subscriber.

This node ensures only verified emails get added to your email marketing list.

Common mistake: Using wrong or expired SendGrid API keys or list IDs, causing failures to add contacts.

Step 5: Add No Operation (NoOp) Node for Invalid Emails

Attach a No Operation node like “Email is not valid, do nothing” to handle the branch for invalid emails cleanly without errors or alerts.

Step 6: Connect All Nodes

Link the workflow edges as follows:

• Form Trigger → Hunter Email Verifier
• Hunter Email Verifier → If (Check if valid)
• If valid → SendGrid Add Contact
• If invalid → No Operation node

This completes your automated email validation and list addition funnel.

Customizations ✏️

• Change form title and description: In the Form Trigger node, modify the formTitle and formDescription fields to suit your brand voice and offer.
• Expand form fields: Add other fields like “Name” or “Company” in the Form Trigger and pass these to SendGrid as additional contact properties.
• Use a different mailing list service: Replace the SendGrid node with another email marketing node (e.g., Mailchimp) and adjust API calls accordingly.
• Enable logging: Add a Set node before SendGrid to log valid emails to a Google Sheet or database for audit purposes.

Troubleshooting 🔧

Problem: “Hunter API request failed or unauthorized”

Cause: Incorrect or missing Hunter API key.

Solution: Go to Credentials → Hunter API in n8n and re-enter your API key. Test connection and retry the workflow.

Problem: “SendGrid fails to add contact”

Cause: Invalid list ID or expired API token.

Solution: Verify your SendGrid API credentials and the list ID used in the SendGrid node configuration.

Problem: “Form submissions are not triggering workflow”

Cause: Webhook URL not correctly set or form data not posting.

Solution: Copy the Webhook URL from the Form Trigger node and replace the form’s submit endpoint with it. Test with a sample submission.

Pre-Production Checklist ✅

• Confirm Hunter API credentials are valid and test API calls in n8n.
• Ensure SendGrid API keys and target list IDs are correctly configured.
• Test the form submission to verify emails flow through entire workflow.
• Verify that invalid emails are correctly filtered and don’t get added.
• Check logs or add debugging nodes if necessary to monitor workflow runs.

Deployment Guide

Once thoroughly tested, activate the workflow on your n8n instance by toggling the switch in the top-right corner.

Make sure the workflow runs continuously on your server or cloud instance.

Monitor runs periodically through n8n’s Execution List for any errors.

Set alerts for key failures if possible through n8n’s error handling options.

FAQs

Can I use a different email verification service?

Yes, you can replace the Hunter node with another email validation API, but you’ll need to update node configurations accordingly.

Does this workflow consume my API credits?

Yes. Hunter io offers 50 free email verifications monthly; beyond that, you need a paid plan.

Is my email list data safe with this workflow?

Your data only flows between your n8n instance, Hunter, and SendGrid under secure API connections. Ensure your n8n instance is properly secured.

Can this scale for high-volume sign-ups?

n8n is scalable, but monitoring API rate limits and usage is important with each service.

Conclusion

In this tutorial, we helped Lucy and you automate the tedious task of verifying and adding valid emails to your mailing list using n8n, Hunter io, and SendGrid. This automation eliminates hours of manual checking, reduces bounces, and enhances your email marketing effectiveness.

By following this step-by-step guide, you now have a hands-free, reliable system ready to keep your subscriber list clean and engaged.

Next steps to explore could be adding personalized welcome emails to new subscribers, integrating Google Sheets for logging submissions, or expanding form fields for richer contact data. Keep automating and growing your business smartly!