I can't access my Library/Mail folder using terminal (line command or scripts) under Sequoia 15.2

I used to rsync my Mail directory to a cloud server (pCloud encrypted). It worked fine up to today when I upgraded from Sonoma to Sequoia (15.2). It seems that the mail folder is protected by the OS, or is it a bug ? The symptom is that I can't run my script or even a line command such as cp or ls to access the content of the Mail folder. I get a "ls: Mail: Operation not permitted" message.

On the other hand, I can have access without any problem using Finder and I can drag and drop any folder within the Mail directory.

Is there something wrong with my filesystem, is it a bug or has Apple decided to (over) protect my files against my will ?

I tried to change the permissions with no success (including with sudo in an admin account). Is there a way to overcome this ? Maybe in the terminal env or as a header in the script ?