If the HTTP status code of the response is 200, among other fields, the response body will contain a confidence level and verbose details.

Confidence Verbose Description
verified verified The mailbox exists, is reachable, and is not known to be illegitimate or disposable.
undeliverable mailboxDisabled The mailbox is disabled.
mailboxDoesNotExist The mailbox does not exist.
mailboxFull The mailbox is full.
syntaxFailure The syntax of the specified email address is incorrect.
internationalCharactersUnsupported The domain does not support the use of international characters (e.g. á, é or ø).
unreachable unreachable The domain is not responding to validation requests or does not have any active mail servers.
illegitimate illegitimate Seed, spamtrap, black hole, technical role account or inactive domain.
roleAccount Role accounts such as support, sales, info etc.
typoDomain The domain of the email address you've provided was close to a common domain and, although it exists, it is highly unlikely to be correct.
localPartSpamTrap Known local portions of the email address that may indicate spam traps.
Profanity The email address contains profanity.
disposable disposable The domain is administered by a disposable email provider (e.g. Mailinator).
unknown unknown We were unable to conclusively verify or invalidate the email address.
timeout The request timed out due to the host domain not responding in time.
acceptAll The domain is accept-all, so the email address cannot be validated.
relayDenied The result was validated at the incorrect mail exchanger.
BLANK You are submitting requests at a faster rate than allowed by the email service providers for the domains you are checking.