Email verification

Also called: Email validation, Email checking, Mailbox verification.

A verifier runs a short pipeline. It checks the address's syntax, looks up the domain's MX records to find its mail servers, then opens an SMTP conversation with one of them. It names the recipient with RCPT TO, reads the reply code, and hangs up before the DATA command, so nothing is delivered. A final test asks about an address that can't exist, to detect catch-all domains.

The result is a grade. A 250 reply on a domain that rejects made-up addresses means the mailbox exists: valid. A permanent 5xx reply such as 550 5.1.1 means no such user: invalid. A server that accepts everything is catch-all. A timeout or a temporary 4xx reply is unknown and should be retried, never marked invalid.

For local lead generation, verification is what separates a list you can send to from a list that burns your domain. Addresses found on small business websites include typos, old staff mailboxes and closed domains, and pattern guesses are often wrong. Sending tools pause campaigns on high bounce rates; Instantly, for example, auto-pauses above 5%.

Verification has limits. It measures one server reply at one moment. It can't tell whether a person reads the inbox, whether mail will land in spam, or anything certain about catch-all domains, and some large providers don't answer checks reliably. Re-verify before a send if the last check is more than about a month old.

Example

A list of 500 dentist emails is verified the day before a campaign: 360 come back valid, 90 catch-all, 30 invalid and 20 unknown. The 360 go out first, the 90 later in a separate batch, the 30 are dropped, and the 20 are re-checked in a few days.

In Leadraft

Every email found is checked against the live mail server and graded Verified, Accept-all or Invalid. Invalid emails are never exported, and a check that fails is never graded invalid: it's retried later.