SpamAssassin rules to be implemented to help reduce SPAM on VestaCP servers.
Credits: http://www.pettingers.org/annoyances/sa-rules.html
Create a new file custom_SA-rules.cf
in the directory /etc/mail/spamassassin/
with the content from custom_SA-rules.cf
Now restart SpamAssassin with
service spamassassin restart