What is an accept-all domain?
An accept-all domain — another name for a catch-all domain — is configured to accept email sent to any address, including ones that don't exist. Because the server never rejects a recipient, you can't confirm an individual mailbox by SMTP alone.
Accept-all and catch-all are the same thing
The terms 'accept-all' and 'catch-all' are used interchangeably. Both describe a mail server that responds positively to every recipient at the domain rather than rejecting unknown addresses. Different verification vendors simply prefer different labels.
The behavior is what matters: a positive SMTP response on an accept-all domain doesn't prove the specific mailbox exists, because the server would have said yes regardless.
Why accept-all domains are common
Companies enable accept-all so that misaddressed mail and departmental aliases still arrive, and many hosting plans turn it on by default. It's especially prevalent on corporate domains, which is exactly where a lot of valuable B2B contacts live.
That prevalence is the challenge: a meaningful share of legitimate business addresses sit on accept-all domains, so you can't simply discard them without losing real prospects.
Verifying addresses on accept-all domains
Since SMTP can't disambiguate individual mailboxes here, the answer is confidence scoring. A verifier evaluates syntax, domain reputation, role-based patterns, and historical signals to estimate how likely the specific address is to be real and deliverable.
Mailbeam detects accept-all domains and returns an AI quality score so you can set a threshold — accepting high-confidence addresses and challenging low-confidence ones — instead of treating the whole domain as valid or invalid.
In practice
lead@enterprise.com is on an accept-all domain, so the SMTP probe returns accept regardless. Mailbeam reports catchAll: true with a score of 84, reflecting clean syntax and a reputable domain — high enough to accept the lead with confidence rather than discarding a real prospect.
Frequently asked questions
Verify emails with confidence
Mailbeam handles all of this for you — syntax, MX, SMTP, catch-all, and disposable checks in one API call. 1,000 free verifications/month, no credit card.