If there is a large spam attack, the antispam daemon spamd starts
too many processes and the system can run out of resources. You can
limit the number of simultaneously running SpamAssassin processes
through the Plesk GUI. Use the The maximum number of worker spamd
processes to run (1-5) option on the Server > Tools & Settings
> SpamFilter page. You can retrieve this value by executing the
following command:
# mysql -uadmin -p`cat /etc/psa/.psa.shadow ` psa -e "select * from misc where param='spamfilter_max_children'"