Catch-All and Unknown Emails Explained
4 min read
When you check a list, most addresses come back Passed or Failed. Some come back Unknown. That is not a mistake. It is the honest answer when the mail server will not say whether a mailbox exists.
What is a catch-all domain?
A catch-all domain accepts mail for any address at that company, whether the mailbox exists or not. If you ask the server whether anything@company.com exists, it says yes to everything. That makes it impossible to tell a real mailbox from an invented one from the outside.
Other reasons for Unknown
- Greylisting: the server asks senders to try again later as an anti-spam step, and does not answer straight away.
- A server that refuses to confirm or deny mailboxes, to protect its users from address harvesting.
- A temporary problem while checking, which can be retried.
Is it safe to send to Unknown addresses?
Sometimes, with care. Unknown means the address might be fine. Many real business emails live on catch-all domains, so throwing them all away loses real leads.
- Send to Passed addresses first.
- Send to a small batch of Unknown addresses and watch the bounces.
- If the bounce rate stays low, send the rest in steps. If it rises, stop and remove the ones that bounced.
Why Unknown results are free here
A credit is used only when the check gives you a clear answer, Passed or Failed. Unknown results are not charged, because you did not get a clear answer.
Paste or upload your list. Only Passed and Failed results use a credit. Unknown results are free.
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