The spamassassin service for systemd lacks a reload function. This is available for OpenRC, but not implemented in the systemd service unit. This should be implemented using: ExecReload=/bin/kill -HUP $MAINPID Furthermore, I think the pidfile should be /run/spamd.pid (not /var/run/spamd.pid), but you might find that off topic here...
+ 01 Feb 2014; Pacho Ramos <pacho@gentoo.org> files/spamassassin.service-r1: + Add an option for reloading and move to /run instead of /var/run (#498716 by + Evert) +