The steps below cover how to enable/disable SpamBox from WHM/cPanel or SSH.
1) Log in to WHM as the root user and navigate to the following location.
WHM > Server Configuration > Tweak Settings
2) Ensure that the following option is enabled. If it is not the setting below will not appear in cPanel.
Enable Apache SpamAssassin™ Spam Box delivery for messages marked as spam (user configurable)
3) Log in to cPanel and navigate to the following page.
cPanel > Email > Spam Filters
4) Toggle the switch next to "Move New Spam to a Separate Folder (Spam Box):"
uapi --user=username Email enable_spam_box
uapi --user=username Email disable_spam_box
uapi --user=username Email get_spam_settings