Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hello Ulysse,
Welcome to the Microsoft Community.
If you are referring to this email address being registered as a Microsoft account and you need to delete or close your Microsoft account, please refer to the following documentation to complete the process and make sure that you have backed up any important data stored in your account before closing it.
How to close your Microsoft account - Microsoft Support
However, the domain name you provided is not an address that can be created or added directly by an individual user. Therefore, I assume that your account is most likely in an organizational environment, and if so, it may be restricted by the organization's IT policies. Since organizational accounts are managed by the organization, please consider contacting the organization's IT staff directly for assistance with deletion.
I hope this is useful.
Best regards,
Ian - MSFT | Microsoft Community Support Specialist