How Verification Works
ReplyLabs validates email addresses by checking multiple signals: DNS MX record existence (does the domain accept email?), SMTP handshake response (does the mailbox exist?), disposable domain detection (is this a temporary email service?), catch-all detection (does the domain accept all addresses?), and syntax validation. Results are returned as a status: deliverable (safe to send), risky (may bounce), or undeliverable (will bounce). Verification uses the No2Bounce API under the hood.
Interpreting Results
Deliverable: the email address exists and is accepting mail. Safe to include in your outreach campaigns. Risky: the address may exist but showed uncertain signals. The domain might be a catch-all or the mailbox may be full. Consider sending but monitor bounce rates. Undeliverable: the address does not exist, the domain has no mail server, or the mailbox is permanently unavailable. Remove these from your list to protect your sender reputation.
Why Verify Before Sending
High bounce rates damage your email sender reputation. Major email providers (Gmail, Outlook) track your bounce rate and will throttle or block your emails if it exceeds 2 to 3%. Verifying your list before outreach ensures you only send to real addresses. This protects your domain reputation, improves deliverability, and saves money on email sending tools.