Definition
A catch-all domain, also called an accept-all domain, is set up so its mail server accepts mail for any address at that domain. Send to [email protected], [email protected] or a random string at company.com, and the server says yes to all of them during the SMTP conversation.
Companies turn this on for different reasons. Some want to make sure misspelled addresses still reach someone. Some route everything into a shared inbox. Others sit behind a security gateway that accepts mail first and decides what to do with it later.
Why it matters
Email verification relies on the mail server telling the truth about a mailbox. When the server accepts every address, that signal disappears. A real employee and a made-up name get the same answer, so nobody, including any verification tool, can confirm that a specific person's mailbox exists.
Some of those accepted messages still fail. The server may accept the mail and then drop it, bounce it later, or hand it to a filter. If a list is full of guessed addresses at catch-all domains, bounces and spam-trap risk go up, and your sender reputation pays for it.
Catch-all addresses are common in B2B lists, so you cannot ignore them. You need a policy for them.
How SimpleCold handles it
SimpleCold runs a catch-all probe once per domain. It asks the mail server about an address that cannot exist. If the server accepts it, the domain accepts everything.
Addresses at those domains come back Risky with the status accept_all and the reason "The domain accepts mail for any address, so this mailbox can't be confirmed." We don't call them Deliverable, because that would be a guess. You see the reason and decide.
A sensible approach is to send to catch-all contacts in smaller batches, prioritise people who have engaged before or whose address came from a reliable source, and watch bounces closely.
You can test any domain with the free catch-all checker.
Related reading
- What a catch-all domain means for your list
- Should you send to catch-all emails?
- Catch-all detection