Question mark in blue box instead of image in emails after upgrading to Monterey?

Mail -> Preferences -> Privacy tab -> Uncheck "Protect Mail Activity" and uncheck Hide IP address and Block All Remote Content. It's a new security option but it breaks things like inline HTML images, etc. The trade off for security is considerable.

Thank You! It works but what am I giving up vs what I had before upgrading? In other words you lose the images with the improved security?

If you turn off the security, you are no worse off than you were in the previous OS.

However, it should not necessarily block the remote content. I don't know why it does so for some but not all.

These are new security features added in Monterey. A lot of spam and marketing email have tracking components such as single pixel image that is referenced on a web server. They can tell when you read the email and track it. There's code as well so there is more to it than just blocking images. Turning the feature on protects your privacy but a lot of HTML email using images will not load as a result.