For some reason Directadmin doesn’t do a periodic update of the SpamAssassin filter rules.
here’s a short howto to run the sa-update command on Directadmin machines, with FreeBSD.
# cpan
cpan> install LWP::UserAgent
cpan> install Archive::Tar
# sa-update --nogpg -D
# killall spamd
# /usr/bin/spamd -d -c -m 5