Agent Email Check (Single Address)

Choose this endpoint when you need a conservative, non-spammy email check that distinguishes between 'definitely invalid', 'probably routable but unconfirmed', and 'confirmed valid via SMTP'. It is especially useful when false positives (treating bad emails as good) are costly — e.g. CRM hygiene, outreach campaigns, or signup validation — and when you want honest uncertainty rather than an optimistic guess. Prefer the optional SMTP probe when a definitive answer is needed and the target domain is not known to block probes.

• Email address is malformed — returns invalid immediately without DNS lookup
• Domain is routable but smtp_check was false — verdict is 'unknown', not 'valid'
• SMTP probe is rate-limited or throttled — only one attempt per target, never retried, may return inconclusive
• Target mail server blocks or graylists SMTP probes — probe result may be unreliable
• Domain does not exist or has no MX records — returns unroutable/invalid