I manage an ISP network with two x1060 and one M670 device.Recently some of the customer's mail are rejected due to ip blacklist,on investigation we found that there is a large number of outgoing spam message from these domains and we confirmed that all outgoing mails are through iroport.
So we decided to enable AntiSpam filtering for outgoing mail messages. please advice me on below questions
1.What is the best methods to enable antispam with minimum false positive?
2. Is it possible to enable spam detection for some domain by creating customised policies?
3.Can we quarantine the detected outgoing spam for a period of thirty days?