What is Email Verification?
Definition: The process of validating whether an email address exists, is deliverable, and is safe to send to, using SMTP checks, domain validation, and mailbox pinging to prevent bounces.
Email verification sits between enrichment and outbound. You found 1,000 email addresses through Apollo or Clay. Before you load them into Instantly and start sending, you need to know which ones will bounce. A bounce rate above 2-3% damages your sender reputation and can get your domain blacklisted.
Verification tools check several things: Does the domain exist? Does the mail server respond? Does the specific mailbox exist? Is the address a known spam trap? Is it a catch-all domain (accepts all emails regardless of address)? The result is a status: valid, invalid, risky, or unknown.
Most GTM Engineers run verification as a step in their Clay waterfall or as a standalone batch process. NeverBounce, ZeroBounce, and MillionVerifier are popular standalone services. Clay and FullEnrich include verification in their enrichment workflows.
The economics are simple. Verification costs $0.003-$0.01 per email. A bounced email costs you sender reputation that takes weeks to rebuild. Run verification on every list, every time. Even if the emails are "verified" by the provider. Providers often verify at collection time but addresses go stale fast. Someone changes jobs, and their old email bounces within 90 days.