mx_unreachable

The mail exchangers could not be reached from the verification network

The probe could not reach any of the domain's mail servers: unreachable at the network level rather than a refused connection.

appears in
smtp_reason
credits
Billed by the verdict it produced: a deliverable answer with smtp_checked false is 1 credit. The settling re-checks are free.

What it means

Transient routing problems and geo-restricted mail servers produce it. The answer is not cached for long, so a later lookup probes again.

What to do

Pass callback_url with the lookup: Spaw re-checks the address after 5 and 20 minutes and pushes the settled verdict to you at no cost. Or re-verify later; repeats inside seven days are free.

Example response

{
    "deliverable": "deliverable",
    "smtp_checked": false,
    "smtp_reason": "mx_unreachable",
    "mailbox_exists": null
}

Abbreviated: a real answer carries all 27 fields, listed in the verify-email reference.

Related

markdown version: /docs/reasons/mx_unreachable.md