NewOutlook · Outlook Desktop
Outlook: Language support for Summarize in Classic Outlook
Outlook users will be able to select a different language for Copilot Summarize responses when the content language differs from their Outlook interface language, improving accessibility for multilingual workflows.
Microsoft's description
When the content language and the Outlook language do not match, you will be able to select a different language to view summarize Copilot responses.