Mailbox Existence Checker
Check whether a specific mailbox exists by asking its mail server over SMTP, with catch-all detection. Free, best-effort — no email is delivered.
Check if a mailbox exists
Enter an email address. We ask its mail server whether the specific mailbox is accepted (SMTP, port 25).
Port 25 must be reachable from the server running this check. No email is delivered — the transaction stops after RCPT TO.
What this mailbox checker does
Common use cases
- 1Confirming a single important address
- 2Checking a mailbox before a critical send
- 3Investigating a suspected bad address
- 4Reducing hard bounces on key contacts
- 5Verifying a support or sales inbox
- 6Spot-checking after list cleaning
Related tools
About mailbox existence checks
An SMTP mailbox check connects to the recipient's mail server and issues the same RCPT TO command a real sender would, reading whether the server accepts or rejects the address — without ever delivering a message.
It is the most direct verification available, but it has real limits, and this tool is honest about them: port 25 must be reachable (many networks block it), servers may greylist or defer, and catch-all domains accept every address so existence cannot be confirmed. Use it for high-value single checks, and rely on the bulk verifier's syntax + MX screening for lists.
More Free Tools Where This Came From
This utility is one of dozens of free, no-login tools for DNS, email, SEO and developers — all instant and private.
HostCloud.in · Pune, India · Serving 34,987+ Websites Since 2020
Got Questions? We Have Answers.
How does it check a mailbox?
It connects to the domain's mail server on port 25 and issues a real RCPT TO command — the same one a sender uses — to see whether the address is accepted, then abandons the transaction so no email is delivered.
Why might the result be inconclusive?
Port 25 may be blocked, the server may greylist or defer, or the domain may be catch-all (accepts every address). The tool reports these honestly rather than guessing.
What is catch-all and why does it matter?
A catch-all domain accepts mail for any address, so it will accept your test even for a non-existent mailbox. When detected, the specific mailbox cannot be confirmed.
Is SMTP verification 100% reliable?
No. Some servers accept all recipients then bounce later, and results vary with greylisting and rate limits. Treat it as a strong best-effort signal, not a guarantee.
Does it send an email?
No. The check stops after the RCPT TO response, so nothing is ever delivered to the mailbox.