If email filtering tools are not tuned based on reported emails, malicious emails will continue to bypass filters.
Effective filtering depends on feedback and updating rules with real threat data.
Flagging legitimate emails (A) would cause false positives, shadow IT (C) and forwarding personal emails (D) are less relevant to the filtering bypass.
Tuning email filters is part of continuous Security Operations processes#6:Chapter 14 CompTIA Security+ Study Guide#.