Log in as user 'arcsight':
1) cd /opt/arcsight/manager/config
2) cp server.properties /tmp/server.properties.bak (this is just to backup the current file in case of problems).
3) Edit the file server.properties and add the following line to the bottom: email.tls.desired=false 4) Save the file
5) Restart the manager service: /etc/init.d/arcsight_services restart manager
Then please test the notification and see if that works