Copilot Chat in Word, Excel, etc but not in Outlook

I have an issue where Copilot Chat is available in all Office applications except Outlook.

Environment:

Windows 11 24H2

Microsoft 365

Microsoft® Outlook® for Microsoft 365 MSO

Version 2510 (Build 16.0.19328.20266)

32-bit

In Outlook, I can see the Copilot button, but the Chat experience is not available.
I only see options like Reply and Summarize when an email is selected.

Additionally, right after starting Outlook, the Copilot button is briefly visible, then it disappears again and only reappears once an email is selected.

Why is the Copilot Chat not available in Outlook, while it works in all other Office applications?