What accept-all means
An accept-all (catch-all) domain is configured to accept mail for every address — real or not. When a server says yes to anything, there is no protocol-level way to confirm whether one specific mailbox exists. That is not a limitation of one tool; it is how the domain chose to behave. Any service claiming to fully verify individual mailboxes on accept-all domains is guessing and labeling it certainty.
We tell you the truth instead: the verdict is accept-all, the domain infrastructure is real and receiving, and the individual mailbox is unverifiable from the outside.
Some large consumer providers — Yahoo, AOL and the ISP domains they run — sit in the same bucket for a different reason: they do reject unknown recipients when they answer, but they will not let an outside checker ask. Those results read provider does not allow verification, which is exactly what happened.
What to do with accept-all addresses
- Treat them as a separate segment — never mixed into your cleanest sends.
- Prefer addresses with engagement history; a past open outweighs any validation.
- Introduce them gradually and let real bounce data prune the segment.
What unknown means — and the refund
An unknown verdict means we could not get a definitive answer in time — a server that never responded, a DNS timeout, an aggressive tarpit. Rather than dress a non-answer up as a result, we mark it unknown and automatically refund the credit when the job settles. You pay for answers, not attempts.
Deep dive: our deliverability guide covers how each verdict protects your sender reputation.