X.7.10 · Security or policy
SMTP enhanced status code 5.7.10
Encryption Needed
X.7.10 means encryption is needed before this authentication or command is allowed, usually TLS via STARTTLS before AUTH PLAIN or LOGIN.
| Registry code | X.7.10 |
|---|---|
| Forms in use | 5.7.10 |
| Registry name | Encryption Needed |
| Subject | 7: Security or policy |
| Permanent or temporary | 5.x.x permanent failure: resending unchanged will not succeed |
| Associated basic codes | 523 |
| Defined in | [RFC 5248] |
What the registry says
This indicates that external strong privacy layer is needed in order to use the requested authentication mechanism. This is primarily intended for use with clear text authentication mechanisms. A client which receives this may activate a security layer such as TLS prior to authenticating, or attempt to use a stronger mechanism.
IANA SMTP Enhanced Status Codes registry, X.7.10
In practice
X.7.10 usually means the client tried to authenticate or send without TLS on a server that requires it. Gmail returns 523 5.7.10 when commands are pipelined after STARTTLS. Use port 587 with STARTTLS or port 465 with implicit TLS, as the provider documents.
What the sender should do
Turn on STARTTLS or SSL in the client settings, using the port the provider documents, and authenticate after the connection is encrypted.
Would verifying the list have prevented 5.7.10?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
How providers use X.7.10
Quoted from each provider’s own error reference.
- Gmail 523 5.7.10
SMTP protocol violation, no commands allowed to pipeline after STARTTLS. For more information, go to About SMTP error messages and review RFC 3207 specifications.
Common questions
- What does 5.7.10 mean?
- X.7.10 means encryption is needed before this authentication or command is allowed, usually TLS via STARTTLS before AUTH PLAIN or LOGIN.
- What should I do about 5.7.10?
- Turn on STARTTLS or SSL in the client settings, using the port the provider documents, and authenticate after the connection is encrypted.
- Would an email verifier have caught 5.7.10?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Sources
- IANA: SMTP Enhanced Status Codes registry (checked 2026-11-05)
- RFC 3463: Enhanced Mail System Status Codes (checked 2026-11-05)
- Google Workspace Admin Help: Gmail SMTP errors and 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