Normalization & syntax
Whitespace cleanup, Unicode normalization, case-insensitive deduplication, IDN domain extraction, structural validation, and original-input preservation.
Domain & MX intelligence
NXDOMAIN, missing and null MX, transient DNS failures, prioritized mail routing, provider fingerprinting, and cached domain evidence.
Mailbox evidence
Optional non-sending SMTP recipient checks, temporary failure handling, mailbox-full signals, policy-block detection, and conservative unknown results.
Catch-all intelligence
Randomized nonexistent-recipient probing when enabled, domain-level caching, explicit detected/not-detected/inconclusive states, and no claim that a catch-all mailbox exists.
Risk signals
Disposable domains, role accounts, gibberish patterns, suspicious structure, common-domain typo suggestions, and risk-aware verdicts.
Provider detection
Google Workspace, Microsoft 365, Yahoo, iCloud, Zoho, Proofpoint, Mimecast, Barracuda, Broadcom, GoDaddy, Mailgun, and custom infrastructure.
Bulk operations
CSV/TXT ingestion, unique-address billing, duplicate counts, background workers, live progress, ETA, partial result inspection, job history, and CSV export.
API & automation
Scoped API keys, single and bulk endpoints, OpenAPI documentation, tenant isolation, rate limits, credit controls, and auditable activity.
Account & billing
Email-code verification, password recovery, protected administration, BTCPay checkout, manual assistance fallback, idempotent fulfillment, and credit ledger.
How statuses work
Valid: decisive positive mailbox evidence is available.Invalid: decisive syntax, domain, or mailbox rejection evidence is available.Risky: risk or catch-all evidence requires customer judgment.Unknown: evidence is unavailable, temporary, blocked, or inherently inconclusive.
What no honest verifier can guarantee
No verifier can guarantee future delivery, inbox placement, engagement, or the existence of an individual mailbox behind a catch-all domain. Receiving systems may intentionally obscure mailbox state, apply reputation policies, greylist, or change behavior. Best Verifier exposes those limitations rather than converting them into false certainty.