About this video

Addresses in this video are examples. File verification needs a paid account.

Video transcript

1. 00:00Nine layers

   Here's every layer an email address passes through before you get a result. Nine layers decide the result. Syntax. Disposable. Labels. DNS. Policy. SMTP. Catch-all. Lookup. And scoring. The first five layers never touch a mail server. And an address can stop early, so later layers never run.

2. 00:23Before the mail server

   Layer one is syntax. We check the email format, leftover URL encoding like %20, and length. Fail here and it's invalid, with no credit used. Layer two compares the domain with a constantly updated disposable list. A match stops the check there, and by default it's free. Layer three only adds labels. A free mail domain. A role name, like info or sales. An alias, like Gmail dots or plus tags. And a typo hint. One label can change the outcome. A valid or catch-all address with a role name ends up as role. Layer four asks DNS where this domain receives mail. No domain, no mail servers, or a record refusing all mail means invalid. But a DNS timeout or server error proves nothing, so that's unknown. Layer five is policy. Apple iCloud, Proton and Tuta don't give a reliable SMTP signal on their own domains. So we don't ask. It's unknown, and it's free.

3. 01:22Ask the mail server

   Layer six is the first one that talks to a mail server. It's on by default. Through the API, check_smtp false turns it off. Layers six to eight are skipped, and most addresses come back unknown. It opens an SMTP conversation. It connects, introduces itself, names this recipient, and reads the reply. No email is ever sent. No such user means invalid. Try again later means unknown, and file jobs retry greylisting on their own. Blocked says nothing about the mailbox, so it's unknown. Mailbox full is unknown too. An accepted reply moves on. A yes isn't always proof, because some domains accept every address. So layer seven also tries a random address that shouldn't exist. If the server refuses it, the yes counts. If it accepts that too, the domain is catch-all. Catch-all only appears when the server accepted your address too. Without that yes, the result is unknown. Layer eight is for some consumer mail providers. A provider account check replaces SMTP. Account found is valid. Not found is invalid. If the check fails, it's unknown, never invalid.

4. 02:33From evidence to a result

   Layer nine recognizes setups like security gateways and forwarding aliases, then applies fixed rules for the status, score and reason. So the score comes from rules. It's not a weighted sum, and it's not a probability. Two steps follow. Domain reputation is an optional API field, for information only. Then caching and billing work out what you pay.

5. 02:57What it costs

   Unknown, bad syntax and disposable are free. Every other result uses one credit, including catch-all and role. Check the same address again within 24 hours, and you won't pay twice, unless you force a refresh through the API. But an unknown that comes back definite uses a credit.

6. 03:13Six outcomes

   So every address ends in one of six statuses. Invalid. Disposable. Role. Catch-all. Valid. And unknown, which isn't a bad address. It means we couldn't get a reliable answer.

7. 03:27Get started free

   20 free credits every day you use your account, up to 600 a month. No credit card required. Start at billionverify.com.