Hi Erwan Tjen,
According to the information you provided above, it may caused by the encoding method.
You can check the encoding method in outlook
How to Change the Character Encoding in Outlook
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
In addition, you can configure the pipeline tracing log in your environment to capture copies of the message.
Detailed information: Pipeline tracing and Configure
pipeline tracing
Regards,
Joyce Shen
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