Hi @Mateusz Gajewski ,
Welcome to our forum!
As i know, you can adjust the ribbon on your Outlook, and the *.officeUI file related to it will be generated on your computer. You can then use the GPO to replace this file. Please refer to this thread and try the suggestion as @Faery Fu-MSFT mentioned:
How to customize Outlook ribbon for multiple users via group policy or registry
Hope to help you!
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