How to Reject Unprofessional Emails in a Webflow Form

Learn how to block consumer email addresses like Gmail and Hotmail in a Webflow B2B form with JavaScript.

In this tutorial, Sandro, cofounder of the Gemeos Webflow agency, shows you how to block consumer email addresses (Gmail, Hotmail, Yahoo...) in a Webflow B2B form.

Example

Test with gmail.com, outlook.com... or a business address

Please use your business email.

✓ Business email accepted!

Approach	Method	Reliability
Domain blacklist	Client-side JS check	Good for obvious cases
Verification API	Emailhunter, Zerobounce	Very high, paid
Business regex validation	Pattern based on the domain	Basic

The script

Add this script to the body of your page. It intercepts the submission and shows an error message if the email comes from a consumer domain.

var BLOCKED = ['gmail.com', 'hotmail.com', 'hotmail.fr', 'outlook.com', 'yahoo.com',
  'yahoo.fr', 'wanadoo.fr', 'orange.fr', 'free.fr', 'laposte.net',
  'icloud.com', 'me.com', 'live.com', 'sfr.fr'];

document.querySelectorAll('form').forEach(function(form) {
  form.addEventListener('submit', function(e) {
    var emailInput = form.querySelector('input[type="email"]');
    if (!emailInput) return;
    var domain = emailInput.value.split('@')[1]?.toLowerCase();
    if (BLOCKED.includes(domain)) {
      e.preventDefault();
      emailInput.setCustomValidity('Please use your business email.');
      emailInput.reportValidity();
    } else {
      emailInput.setCustomValidity('');
    }
  });
});

Customize the blacklist

Add or remove domains from the BLOCKED array depending on your industry. Some companies allow Gmail Workspace (a business email on a custom domain): make sure you don't block real business emails that use Gmail in the backend.

good to know

This validation is client-side only: a savvy user can bypass it. For robust validation, reinforce it on the server side (via an n8n or Zapier webhook that checks the domain before adding the contact to your CRM). JS validation is still useful for reducing accidental mistakes and improving UX.

Conclusion

This snippet cuts down on noise in your CRM and improves the quality of your B2B leads. See also: Webflow anti-spam honeypot.

Good to know

Heading

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