What Is a Catch-All Domain?
TL;DR
A catch-all domain is a domain configured to accept mail for every address at it, including addresses with no mailbox behind them. Because the server accepts anything, an SMTP verification probe cannot separate a real mailbox from a typo, so verification tools report catch-all or accept-all rather than valid or invalid.
Why can a catch-all address not be verified?
Verification works by starting an SMTP conversation and reading how the receiving server answers the recipient command. A normal server refuses an address with no mailbox, and that refusal is the signal. A catch-all server answers yes to every recipient, so the probe learns only that the domain exists.
The address may still be perfectly real. Catch-all is a statement about the receiving configuration, not about the person, which is why treating every catch-all result as invalid discards a large part of the reachable audience at exactly the companies most likely to be worth contacting.
Should you send to catch-all addresses?
Yes, as a separate risk tier rather than mixed into the main list. Keep them out of a domain that is still warming, send them in small batches from an established sender, and watch what comes back, since a catch-all server can accept a message and then discard it or produce a delayed bounce hours later.
Pattern beats guessing on these. A first-initial-plus-surname convention confirmed on two known addresses at a company is a far better bet on a catch-all domain than a generic role address, which reaches a shared mailbox nobody owns.
Frequently asked questions
No. A role address such as info@ or sales@ is a real mailbox belonging to a function rather than a person. Catch-all describes the server accepting any local part at all, so a catch-all domain can hold named mailboxes, role mailboxes and nothing, all answering the same way.