Forwarded Email Encoding Changed from UTF-8 to ISO-2022-JP

Syafiq Fadzli 0 Reputation points
2026-08-24T02:19:39.1+00:00

Hi, I am using an email forwarding rule in Outlook to forward emails to another email address.

However, I noticed that for emails containing Japanese characters, the character encoding is automatically changed to charset="iso-2022-jp", even though the original email was encoded in UTF-8.

This causes an issue when I need to download the received email in HTML format. When I open the downloaded HTML file in a web browser, the Japanese characters are displayed as garbled text.

I have checked the available Outlook settings but could not find any setting that would cause the character encoding to be changed to iso-2022-jp.

Could you please help me identify where this encoding conversion is occurring and whether there is a way to prevent Outlook/Exchange from changing the original UTF-8 encoding?

This issue has been ongoing for some time and is affecting our email processing, so I would greatly appreciate your assistance.

Exchange | Exchange Server | Other
Exchange | Exchange Server | Other

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  1. Hani-Ng 1,130 Reputation points Independent Advisor
    2026-08-24T02:54:58.45+00:00

    Hi Syafiq Fadzli

    Since you are using Exchange Server, the encoding change is most likely occurring during Exchange transport content conversion, rather than in Outlook. Exchange can re-encode messages when processing forwarded mail, and Japanese messages may be converted from UTF-8 to ISO-2022-JP depending on the message format and Remote Domain settings.

    Could you please run the following command and share the output?

    Get-RemoteDomain | fl Name,DomainName,CharacterSet,NonMimeCharacterSet,ContentType

    Also, please provide the relevant portions of the Internet headers from both the original and forwarded messages, including:

    Content-Type

    charset=

    Content-Transfer-Encoding

    If the original message shows charset="utf-8" and the forwarded message shows charset="iso-2022-jp", Exchange is likely performing the conversion during transport.

    Please also note that Exchange Server may perform content conversion when forwarding messages. As a result, the MIME structure or character encoding of a forwarded message may not always be preserved exactly as received. Further review of the message headers and Exchange configuration will help determine whether this is occurring in your environment.

    To better understand the scenario, could you also provide:

    • Exchange Server version and CU level
    • How forwarding is configured (Inbox Rule, Mailbox Forwarding, or Transport Rule)

    This information will help determine whether a Remote Domain configuration or Exchange transport setting is causing the UTF-8 to ISO-2022-JP conversion.

    For your informatrion, you can refer to:

    Content conversion | Microsoft Learn

    Message encoding options in Exchange Server | Microsoft Learn

    I hope this information helps and look forward to your response.

    Note: Please follow the steps in the forum documentation to enable e-mail notifications if you want to receive the related email notification for this thread.  

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