Developing a business case to replace the system is the FIRST course of action that the information security manager should take, because it helps to justify the need for a new and effective email filtering system that can prevent or reduce phishing incidents. A business case should include the problem statement, the proposed solution, the costs and benefits, the risks and assumptions, and the expected outcomes and metrics.

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CISM Review Manual, 16th Edition, ISACA, 2020, p. 42: “A business case is a document that provides the rationale and justification for an information security investment. It should include the problem statement, the proposed solution, the costs and benefits, the risks and assumptions, and the expected outcomes and metrics.”

Email Filtering Explained: What Is It and How Does It Work: “Email filtering is a process used to sort emails and identify unwanted messages such as spam, malware, and phishing attempts. The goal is to ensure that they don’t reach the recipient’s primary inbox. It is an essential security measure that helps protect users from unwanted or malicious messages.”

Cloud-based email phishing attack using machine and deep learning …: “This attack is used to attack your email account and hack sensitive data easily.”