The local part provides structural clues: syntax errors, likely provider misspellings, plus tags, and shared role names. The domain provides public evidence: mail routes, provider classification, registration events, and sender-authentication records. Combining those layers is useful for reviewing signups or troubleshooting a suspicious address, but it does not reveal private inbox state.
Mailbox verification requires the recipient to prove control, usually by clicking a link or entering a code. SMTP recipient probes are unreliable because major providers deliberately hide whether an inbox exists. Sending history is equally private; this tool has no access to complaint rates, personal correspondence, or a provider's internal abuse model.
Choose the narrower tool when you can
If you only need formatting and routing, use the email validator. If temporary providers are the concern, use the disposable email checker. The email leak checker is a separate, opt-in breach query because it must transmit the complete address to its data provider.
For automated decisions, retain the individual findings rather than copying the overall label. A null MX is conclusive about receiving mail; a new domain or missing DMARC policy is not conclusive about intent. Those differences matter when a warning affects a real user.