How to move/rename user mbox file with mailutils?

Is there a way to change the ~/mbox file where mailutils's mail program saves read mail and where mail -f reads from to something else, like ~/.mbox for example? I read that setting the MBOX environment variable does this but I tried setting it to both ~/.mbox and $HOME/.mbox and neither did anything for me. For reference, I tried setting MBOX both just by setting it in the current terminal session and by using the env command, and neither worked.