EmailShield Docs

Every cold email setup has four parts

EmailShield is part 4: the last check before you send. It looks at every address on your list, asks its mail server whether the mailbox exists — without sending an email — and tells you which ones are safe to send to.

Part 1 Infrastructure Maildeck Domains and inboxes you send from Part 2 Sequencer Instantly, PlusVibe… Sends emails and follow-ups Part 3 Leads LeadSonar The right people and their emails Part 4That's us Verification EmailShield Removes bad addresses first

Start here

Cold email in 5 minutes The four parts, and why verifying your list protects your domains.

Your first list in 10 minutes Sign up, upload a CSV and download the clean version.

Credits and plans What a credit buys, what's free, and what's refunded.

Reading your results Safe to send, risky and invalid — and what to do with each.

Understand every answer

Every status explained Valid, catch-all, role, disposable, spam trap, no mail server and the rest.

Catch-all addresses Domains that accept everything, and how EmailShield rates them.

Why some results are unknown When a mail server won't answer — and why you're not charged for it.

How verification works What happens to an address between upload and verdict.

Build it into your own tools

REST API

Verify one address or 50,000 per call, poll the job, page through results, get a signed webhook when it’s done. One API key, JSON in and out.

API overview →

For AI agents

Plain-text versions of these docs for assistants and agents, and the rules an agent should follow before it spends credits.

EmailShield for AI agents →

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