A catch-all (or accept-all) domain is one whose mail server accepts email sent to any address at that domain, whether or not a mailbox exists. anything@company.com is accepted and sorted out later.
Why it matters for cold email
Email verification works by asking the mail server whether a mailbox exists. A catch-all server says yes to everything, so a verifier can't tell a real address from a guess. Some of those addresses are real people; others bounce later or are never read.
How to handle them
- Send to confirmed addresses first.
- Send to catch-all addresses in smaller numbers, and watch the bounce rate.
- Prefer the company's most common address pattern, such as
first.last@, over unusual guesses.
Google Workspace and Microsoft 365 reject unknown addresses by default; catch-all is more common with forwarding services and self-hosted mail servers.
How to tell if a domain is catch-all
A verifier asks the domain's mail server about an address that can't exist. If the server accepts that too, the domain accepts everything, and every address on it is marked catch-all. You can't settle it by sending, because an accepted email may never be read.
Should you send to them?
Only in small numbers, after your confirmed addresses, while the bounce rate stays under 2%. If it climbs, leave the rest of the catch-all addresses out.