Definition
Email verification: Checks whether a specific mailbox exists and accepts mail, usually through a live SMTP conversation with the recipient server that stops before any message is sent. Verification services add risk signals such as catch-all, disposable and role-based detection.
What an email verification check includes
Syntax and typo checks come first, then DNS: does the domain exist and does it have mail servers. Next come screens for disposable domains and role addresses, which are valid but carry risk.
Then the live part: an SMTP conversation with the domain's mail server that asks about the mailbox and stops before any message is sent, plus a catch-all test to see whether the server says yes to everything.
When to verify email addresses
At capture, through an API call or a form widget, so bad addresses never enter your system. Before importing any list you did not build yourself.
Before any send to a segment you have not mailed in a few months, because addresses decay on their own. And on a schedule for lists you mail rarely.
What email verification results mean
Deliverable: the mailbox exists and accepts mail, so send. Undeliverable: no mailbox, a dead domain, bad syntax or a disposable domain, so remove.
Risky: the address works but carries risk, such as a catch-all domain or a role inbox, so decide by segment. Unknown: the server gave no clear answer, so retry later.
How RocketVerifier handles it
Every address runs through syntax, DNS and MX, disposable and role screening, catch-all analysis and a live SMTP handshake, with 99.5% accuracy. The API typically answers in under 400ms, or 1 to 3 seconds when a live SMTP check is needed, and bulk jobs run at up to 100,000 emails per hour. Each verification uses 1 credit, unknown results and duplicate addresses are never charged, and pay-as-you-go credits never expire.