I am running Microsoft 365 Personal using Outlook Classic on a Windows 11 PC and updated the Software yesterday morning and the Co-Pilot menu was gone from Outlook.
I had already disabled Co-Pilot in the other apps Excel, Power Point, Word etc.
The overwhelming majority of feedback I saw on a Microsoft Board was that people were not happy that they were not given a choice to turn off Co-Pilot in Classic Outlook, yet you could in the new Outlook.
On the Microsoft Board there was a recent post by a Microsoft Rep that they were going to test an Outlook Classic Build without Co-Pilot on an Insider Build and if all went well it would be released around September. I don't know what has happened I am definitely not running an Insider Build.
There is another thread on the this Board Re Co-Pilot which I posted about Co-Pilot button in Outlook Classic being gone after I updated yesterday and a response from a poster that was running the Version of Outlook as me still had the Co-Pilot Button in his Outlook.
Microsoft are rebranding no Co-Pilot versions of 365 to Microsoft 365 Personal or Microsoft 365 Family Classic.