5.6.2: conversion needed but not allowed
The content would have to be converted to be delivered, but the message itself or the sending host's policy forbids that conversion.
- Standard
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.6.2
- Provider
- Standard SMTP codes
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
5.6.2 Conversion required and prohibited
What it means
Some paths need content changed on the way, for example 8-bit text turned into a 7-bit encoding, or a format converted for a gateway. X.6.2 says such a conversion was required and that the message or the sending host's policy prohibits it. RFC 3463 ties it to no class, but the same conversion would be needed on every attempt, so it is listed here as 5.6.2 and the message is returned. The way through is to send it in a form that needs no conversion, usually with standard encodings for every part.
Common causes
- A message marked as not to be converted, sent along a path that requires conversion.
- A sending host policy that forbids changing message content in transit.
How to fix it
- 01Send every part of the message with a 7-bit safe encoding (base64 or quoted-printable).
- 02Check whether your software or a signing step asks servers not to alter the content.
- 03Ask the recipient's administrator whether a route without conversion is available.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 5.6.3Conversion needed but not possible.The content has to be converted before it can be passed on, but a server on the path is not able to perform that conversion.
- 5.6.1Content type not supported.The message uses a kind of content that the delivery protocol or the next system on the path cannot carry, so it was refused.
- 5.6.5Conversion failed.A server tried to convert the message content so it could be delivered, and the conversion did not succeed.
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