Verifies one or more addresses (up to 100) BEFORE writing to them, without sending anything: syntax, a domain that receives mail, a mailbox that already hard-bounced on Mailcheer, disposable or role mailboxes, and DNS signals of a dead mailbox. Each address gets a verdict: invalid (writing to it will bounce), risky (may bounce, or is not a person), unknown (DNS did not answer) or valid (nothing known against it — not a proof that the mailbox exists). Use it before prospecting, or before importing a list you did not collect yourself.