implicit_mx
The domain has no MX record and relies on the address-record fallback
No MX record exists; by the letter of RFC 5321 mail would be delivered to the host at the domain's A record, which is almost never a mail server today.
- appears in
- reason
- verdict
- risky
- risk weight
- +30
- credits
- 1 credit, like every deliverable or risky answer. Repeats of the same address are free for 7 days.
What it means
RFC 5321 says that a domain without MX records receives mail at its A or AAAA address. Real mail domains stopped relying on that decades ago: a web server answering on port 80 does not accept mail. Spaw reports mx_found true and mx_implicit true, and flags the address as risky.
The mailbox handshake still runs. If the host really does accept mail, the probe can confirm or reject the mailbox and the verdict follows that answer.
What to do
Treat the address as probably dead unless the handshake confirmed the mailbox. On B2B lists it usually marks a company that lost its mail setup or a domain used only for a website.
Example response
{
"email": "[email protected]",
"deliverable": "risky",
"reason": "implicit_mx",
"mx_found": true,
"mx_implicit": true
}Abbreviated: a real answer carries all 27 fields, listed in the verify-email reference.
Related
- likely_typo · the domain is a known misspelling of a real mail provider
- disposable · the domain belongs to a disposable, temporary email provider
- mailbox_full · the mailbox is over its storage quota
- role · a shared role inbox such as info@ or support@ rather than a person
- catch_all · the server accepts every address at the domain, so the mailbox cannot be confirmed
- All verdict reasons
- Verdicts and the risk score
- API reference
markdown version: /docs/reasons/implicit_mx.md