How to verify a work email before you send

A guessed address — first.last@company.com — is a bet, not a fact. Real verification connects to the domain’s mail server and asks whether that specific mailbox exists: the same handshake a real email would trigger, stopped one step before delivery. That’s different from checking that an address just looks well-formed, or that the domain has an MX record at all — both pass for almost any address at almost any company, guessed or not.

Three levels, only one of them means anything

Syntax validation checks the address has an @ sign and a domain-looking string after it. It catches typos, nothing else. Domain validation checks the domain has an MX record, so mail could theoretically be delivered there — but says nothing about any specific mailbox on it. Mailbox verification is the only level that actually asks the receiving mail server whether this exact address exists, via the same SMTP conversation a real send would start. If a tool only does the first two and calls the result “verified,” it’s guessing with extra steps.

The catch-all wrinkle

Some domains accept mail to any address — a deliberate configuration, not a bug — which means the mail server will say yes to a guess and a typo alike. No verification method, ours included, can confirm a specific mailbox on a catch-all domain; the honest response is to say so and hand back the best pattern match as unconfirmed, rather than reporting it as verified. See why “verified” finders often aren’t for more on this.

Why it matters more than list size

A list of 1,000 guessed addresses that’s 60% accurate will bounce roughly 400 times. Past a domain- specific threshold — usually cited around 2–5% — mailbox providers start treating the whole sending domain as suspect, not just the individual bad addresses. See what a high bounce rate actually costs you for the mechanics. A smaller, verified list outperforms a bigger guessed one almost every time, because the guessed one is quietly spending your domain’s reputation to find out which addresses were real.