Email verification

A verifier checks the address's syntax, looks up the domain's MX records to see that it accepts mail, and then talks to the receiving mail server to ask whether the mailbox exists, stopping before any message is sent. The answer is usually valid, invalid, unknown or catch-all.

Verification protects your sender reputation. Sending to addresses that do not exist produces hard bounces, and mailbox providers read a high bounce rate as a sign of a careless or purchased list. Because people leave jobs and mailboxes are closed, an address that was valid months ago may not be valid today, so verification has a shelf life and should be repeated close to the send. Addresses at catch-all domains cannot be confirmed this way, because the server accepts every address, and are better skipped or treated with care.

• In Outlevo: An email goes only to an address verified valid in the last 30 days