X.6.2 · Message content or media
SMTP enhanced status code 5.6.2
Conversion required and prohibited
X.6.2 means the content had to be converted to be delivered but conversion was prohibited, by the sender or by the sending host's policy.
| Registry code | X.6.2 |
|---|---|
| Forms in use | 5.6.2, 4.6.2 |
| Registry name | Conversion required and prohibited |
| Subject | 6: Message content or media |
| Permanent or temporary | 4.x.x persistent transient failure: retrying later may succeed; 5.x.x permanent failure: resending unchanged will not succeed |
| Associated basic codes | Not given |
| Defined in | [RFC 3463] |
What the registry says
The content of the message must be converted before it can be delivered and such conversion is not permitted. Such prohibitions may be the expression of the sender in the message itself or the policy of the sending host.
IANA SMTP Enhanced Status Codes registry, X.6.2
In practice
X.6.2 means a conversion was needed and was forbidden, either by a header the sender set or by local policy. It is mostly seen between servers with different 8-bit support. Encoding content as 7-bit MIME before sending removes the need for conversion. Some gateways also refuse to convert content that is signed, because conversion would break the signature, so signed 8-bit mail is a common case.
What the sender should do
Allow conversion or send the content in a form the next hop accepts, such as 7-bit encoded MIME.
Would verifying the list have prevented 5.6.2?
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.
Common questions
- What does 5.6.2 mean?
- X.6.2 means the content had to be converted to be delivered but conversion was prohibited, by the sender or by the sending host's policy.
- What is the difference between 5.6.2 and 4.6.2?
- They share the subject and detail digits, so they report the same condition, "Conversion required and prohibited". The first digit is the class: 4.x.x persistent transient failure: retrying later may succeed; 5.x.x permanent failure: resending unchanged will not succeed.
- What should I do about 5.6.2?
- Allow conversion or send the content in a form the next hop accepts, such as 7-bit encoded MIME.
- Would an email verifier have caught 5.6.2?
- 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)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05