X.7.18 · Security or policy
SMTP enhanced status code 5.7.18
Domain owner has changed
X.7.18 means the recipient's domain has changed owner since the date you gave in a Require-Recipient-Valid-Since check.
| Registry code | X.7.18 |
|---|---|
| Forms in use | 5.7.18 |
| Registry name | Domain owner has changed |
| Subject | 7: Security or policy |
| Permanent or temporary | 5.x.x permanent failure: resending unchanged will not succeed |
| Associated basic codes | 5XX |
| Defined in | [RFC 7293] |
What the registry says
This status code is returned when a message is received with a Require-Recipient-Valid-Since field or RRVS extension and the receiving system wishes to disclose that the owner of the domain name of the recipient has changed since the specified date-time.
IANA SMTP Enhanced Status Codes registry, X.7.18
In practice
X.7.18 is the domain-level version of X.7.17: the domain changed owner after the date the sender gave. It catches mail to addresses on lapsed and re-registered domains. Remove those addresses, since whoever owns the domain now is not your contact.
What the sender should do
Remove addresses on that domain from lists collected before the change.
Would verifying the list have prevented 5.7.18?
Partly
The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Common questions
- What does 5.7.18 mean?
- X.7.18 means the recipient's domain has changed owner since the date you gave in a Require-Recipient-Valid-Since check.
- What should I do about 5.7.18?
- Remove addresses on that domain from lists collected before the change.
- Would an email verifier have caught 5.7.18?
- Partly. The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Sources
- IANA: SMTP Enhanced Status Codes registry (checked 2026-11-05)
- RFC 3463: Enhanced Mail System Status Codes (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05