Catch-all

A catch-all (or accept-all) domain accepts messages for addresses that are not real mailboxes. Mail to sales@, random strings@, and typos all land somewhere instead of bouncing.

That is handy for small teams and awkward for list quality. You cannot tell from SMTP alone whether an address is a real person. Validators often mark catch-all domains as “unknown” because the server accepts everything.

If you market to addresses on catch-all domains, expect more noise and fewer clear hard bounces. Prefer confirmed opt-in and real engagement over “it accepted the RCPT TO.”