How to use it
Enter one address and select Check address. The result is one of four verdicts, followed by the individual checks that led to it. If the domain looks like a common misspelling (for example gmial.com), you can re-check the corrected address in one click.
What it checks
Syntax
The address must have exactly one @, a part before it of at most 64 characters, and a domain with valid labels and a real top-level domain. Dots cannot start, end or repeat in the part before the @. The full standard allows some exotic forms, such as quoted local parts, that real mailboxes essentially never use; the checker treats those as invalid for outreach purposes.
Domain mail setup
Your browser looks up the domain's MX records over DNS-over-HTTPS. If there are MX records, the domain is configured to receive mail. If the domain does not exist, publishes a "null MX" (an explicit statement that it accepts no mail), or has no MX or address records at all, nothing sent there can be delivered. A domain with only an address (A) record is flagged as risky.
Risk hints
- Role addresses such as
info@,sales@orsupport@usually reach a shared inbox rather than a person. - Disposable domains are throwaway inboxes. The built-in list covers well-known services only.
- Typos in popular consumer domains and endings such as
.conare caught and corrected. - Free providers such as Gmail or Outlook.com are noted, since in B2B outreach a personal address may not be the right contact.
What it does not check
This tool does not verify that the mailbox itself exists. That requires connecting to the receiving mail server and asking whether it would accept mail for the address, an SMTP conversation browsers cannot have. Even dedicated verification services get an "unknown" answer for many business domains, because catch-all servers accept every address and only bounce later. A "valid address on a domain that accepts mail" result means the address is plausible, not that it is guaranteed to deliver.
Why it matters
Every bounce tells mailbox providers your list may be stale or bought, and a high bounce rate damages sender reputation for every later message from your domain. Catching malformed addresses, dead domains and typos before a send is the cheapest fix there is. For larger lists, run a mailbox-level verification service as well, and remove addresses that hard-bounce rather than retrying them.
Next, make sure your own domain is set up correctly with the email deliverability checker, and review your copy with the spam word checker.