If you want Amavisd to insert X-Spam-* headers in each email, please decrease Amavisd setting $sa_tag_level_deflt (in Amavisd config file )to a very low score, e.g. -999, then restart Amavisd service:
$sa_tag_level_deflt = -999;That means Amavisd will insert X-Spam-Flag and other X-Spam-* headers when email score >= -999.
Do not forget to restart services Amavisd.
Enjoy.