OpenSMTPD + rspamd to sign mail.

Hello

After:
# pkg_add redis rspamd opensmtpd-filter-rspamd successfully

i got:
# rcctl start rspamd
rspamd(failed)

then I did:
# rspamd -d
2021-08-12 09:23:41 #0(main) <f417f0>; main; detect_priv: cannot run
rspamd workers as root user, please add -u and -g options to select a
proper unprivilleged user or specify --insecure flag

How to interpret it please?

I did # chown R spamd:_rspamd /etc/mail/dkim but it fails, then i did
# chown -R root:_spamd /etc/mail/dkim and it worked; anyway i suppose i
should do rspamd:_rspamd to change -u and -g

thanks for your attention.