Login in the server
Follow the below instruction
mtracks#cd /etc/mail/spamassassin/
mtracks#ls -l local.cf
Note down the permission and ownership of the file local.cf
mtracks#vi local.cf
add the line on the file local.cf " blacklist_from         emailid(ex: info@123.com) "
Save the file and try send a mail in that id through telnet and check in the logfile
that in Amavis there will be some score (ex:92.96) given that email id by spam.