Ho provato a cambiarlo, ma non me lo permetteva.
# ls -dZ /usr/local/spamassassin
drwx------. spam spam system_u:object_r:usr_t:s0 /usr/local/spamassassin
# chcon -v --type=spamd_t /usr/local/spamassassin
changing security context of `/usr/local/spamassassin'
chcon: failed to change context of `/usr/local/spamassassin' to `system_u:object_r:spamd_t:s0': Permission denied
audit.log
type=AVC msg=audit(1483587389.449:354941): avc: denied { append } for pid=31588 comm="spamd" name="spamfilter.log" dev=xvde ino=24109 scontext=unconfined_u:system_r:spamd_t:s0 tcontext=unconfined_u:object_r:usr_t:s0 tclass=file
CentOS versione 6.8 (finale)