Email Checker

Four independent layers. Syntax: the address matches valid email structure (necessary, proves nothing about existence). Domain: DNS confirms the part after @ is a registered, resolving domain. Mail servers: the domain publishes MX records — the machines that accept its mail; no MX (and no fallback address) means mail physically cannot be delivered there. Disposable: the domain matches known temporary-inbox services. A pass on all four means mail sent there will be accepted by a real mail system — the strongest claim honest verification can make.

Because confirming a mailbox requires asking its mail server mid-SMTP-conversation ('RCPT TO: this user?'), and modern providers deliberately refuse to answer honestly: catch-all domains accept every address whether or not it exists, Gmail and Microsoft return acceptance regardless and sort later, and servers that do answer honestly get harvested by spammers — which is exactly why the behavior died. Paid 'verification' services run these SMTP probes anyway and return probabilities dressed as certainty. The only true mailbox test is sending a message that requires a reply or click.

Services like Mailinator or 10minutemail hand out instant, often public, short-lived inboxes — legitimate for dodging newsletter spam, problematic when you need a lasting contact (the address may be unreadable within the hour, and many are readable by anyone who guesses the name). This checker flags the well-known domains; be aware the ecosystem churns new domains constantly, so detection is a strong filter, not a complete one. If you run signups: flag rather than block — disposable users often convert to real addresses when asked at the right moment.

Use it for the mechanical layer — spot-checking important addresses, catching typos before they bounce, and understanding why an address fails — but know the economics of scale: bulk sending to bad addresses causes bounces, and bounce rates above ~2% damage your sender reputation with mailbox providers. For lists in the thousands, that means dedicated verification services (probabilistic, but built for volume) plus the practices that matter more: confirmed opt-in at signup (which prevents bad addresses ever entering), and pruning subscribers who haven't opened in a year.