Real-Time Email Verification at Signup: A Developer Guide

Adding real-time email verification to your signup form is one of the best investments you can make in your data quality. It stops bad emails before they ever enter your database.

Why Verify at Signup?

• Prevents typos and fake emails from entering your list
• Reduces bounce rates from day one
• Saves money on verification later (fix it at the source)
• Improves user experience (catches typos users want corrected)

Integration Example

Here's how to add real-time verification using the CheckMail1 API:

// Frontend: validate on blur
document.getElementById('email').addEventListener('blur', async (e) => {
  const email = e.target.value;
  const res = await fetch('/api/check-email', {
    method: 'POST',
    headers: {'Content-Type': 'application/json'},
    body: JSON.stringify({ email })
  });
  const data = await res.json();
  if (!data.valid) {
    showError('Please enter a valid email address');
  }
});

// Backend: Node.js route
app.post('/api/check-email', async (req, res) => {
  const { email } = req.body;
  const result = await axios.get('https://checkmail1.com/api/verify', {
    params: { email },
    headers: { 'X-API-Key': process.env.CHECKMAIL_API_KEY }
  });
  res.json({ valid: result.data.valid && result.data.score > 70 });
});

What Score Threshold to Use

• Score > 80 — strict, for transactional email lists
• Score > 70 — balanced, recommended for most use cases
• Score > 50 — permissive, catches only clearly invalid addresses

Start with 70 and adjust based on your signup conversion data.