Use Case · Best Practices 2026
How to Verify Emails for Cold Email Outreach
Cold email campaigns live and die by deliverability. A bounce rate above 2% signals spam behaviour to inbox providers — causing your domain to be throttled or blacklisted. Email verification eliminates hard bounces before your campaign goes live, protecting the sender reputation you've spent months building.
The Cold Email Deliverability Problem
Spam complaints and bounce rates are the two fastest ways to destroy a sending domain. Both are driven by the same root cause: unverified email addresses in your outreach list. The consequences compound — once blacklisted, you're not just missing opens, you're paying for sends that never arrive.
- !Purchased or scraped lead lists contain 15–30% invalid addresses on average
- !A hard bounce rate above 2% triggers spam filters at Google, Microsoft, and Outlook
- !A blacklisted sending domain can take 3–6 months to fully recover deliverability
- !Role-based addresses (info@, sales@, admin@) go to ticketing systems, not decision-makers
- !Disposable addresses waste sending credits and distort open-rate and reply-rate metrics
How Our API Solves This
Run every address in your outreach list through our API before import. We validate MX records, perform an SMTP handshake, detect disposable domains, and flag role-based accounts — returning a confidence score and detailed flags so you can make nuanced filtering decisions, not just a binary valid/invalid.
// Verify a cold email list before campaign launch — Node.js
const leads = ["ceo@company.com", "info@company.com", "temp@mailinator.com"];
const results = await Promise.all(
leads.map(email =>
fetch("https://api.emailverify.io/verify", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ email, api_key: "ev_..." })
}).then(r => r.json())
)
);
// Keep only valid, non-role-based addresses with high confidence
const cleanList = results.filter(
r => r.valid && !r.details.role_based && r.score >= 0.85
);
console.log(`Sending to ${cleanList.length}/${leads.length} addresses`);See the full API documentation for all response fields and language examples.
Cold Email Verification Best Practices
Verify within 48 hours of sending, not just at list import
Email addresses decay at roughly 2.5% per month. A list cleaned 6 months ago may have 15% invalid addresses. Always re-verify within 48 hours of a campaign launch.
Filter out role-based emails before sending
Addresses like info@, support@, admin@, and sales@ route to team inboxes or helpdesk queues — never to an individual. Use the role_based flag to remove them from outreach sequences.
Set a minimum confidence score threshold of 0.85
Don't rely on the valid boolean alone. Our 0–1 confidence score lets you filter borderline addresses. Scores below 0.85 often indicate real-but-risky addresses better excluded from cold campaigns.
Use only score > 0.95 addresses during domain warm-up
During the first 4 weeks of warming a new sending domain, even a 1% bounce rate can derail your reputation. Restrict outreach to the highest-confidence addresses only.
Re-verify after 90 days of list inactivity
Addresses that haven't been emailed in 90 days are significantly more likely to have churned. Run a verification pass before any re-engagement campaign to prevent sudden bounce spikes.