Email verification
Checking whether an email address is valid and can receive mail before sending to it: syntax, domain and MX records, and sometimes a probe of the receiving server.
What it means
Verification services typically check syntax, whether the domain exists and accepts mail (MX records), known disposable and role addresses, and often whether the mailbox exists by starting an SMTP conversation without sending a message. That last check is limited by design: RFC 5321 lets servers disable the VRFY command for security reasons and answer 252 instead, and M3AAWG notes that some mail is rejected asynchronously, hours or days later, especially B2B mail, so a probe can report an address as valid that later bounces.
M3AAWG recommends validating an address as it is entered and asking the subscriber to re-enter it if validation fails. Confirmed opt-in is the stronger check, since it proves the owner can receive and wants the mail.
Verification removes bad addresses; it does not create consent or detect most spam traps.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
All 432 terms in the glossaryThe wiki: blocklists and bounce codes