MBP, I have numerous times. For anyone else who might come across this issue, turns out it was Avast antivirus causing the issue. It’s possible their mail protection is conflicting with Apple’s privacy protection somehow. Or maybe just not fully compatible with Monterey.
Does Malwarebytes actively scan your emails though? I know Avast has a feature specific to it so that explains my problem. For me, nothing would make the email body show besides disabling Avast email protection, even creating a new user still had the same result.
Potential Solution Confirmed: I had exactly the same problem on my 2020 M1 Mac Mini running Monterey (but not on my 2018 Macbook Pro running Big Sur). For my case, I found a solution. As FlameLegend also indicated, I discovered that my antivirus app -- Avast Premium Security -- had the Email Shield turned on. When I turned it off and restarted Mail, all of the mail bodies populated. Then I turned Email Shield back on and again restarted Mail. The email bodies disappeared again. So for my configuration, Avast has some incompatibility with Monterey. Interestingly, this issue of email body snatching only happens with iCloud. It does not happen with my other email services.
