How-to guidesUpdated 5/13/2026
How to verify emails before sending (and why deliverability depends on it)
Sending a cold-email campaign to an unverified list is the #1 way to wreck your sender reputation. Every bounce damages your domain's standing, dropping inbox placement for future sends. Verifying before send is mandatory for serious outbound.
What verification checks
Three layers, each catching different invalid emails.
- Syntax — basic regex (catches @gmial.com typos)
- MX records — domain has working mail servers (catches dead domains)
- SMTP handshake — low-level RCPT TO probe without sending (catches non-existent mailboxes)
- Catch-all detection — flags domains accepting everything
Why catch-alls are a trap
A catch-all accepts every <anything>@<domain>. Verification marks them deliverable, but in reality most go to spam folders or hard-bounce later. Kavex flags catch-all results explicitly so you can choose to skip them.
Tools mentioned in this guide
How Kavex compares to alternatives
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