Email providers make filtering decisions based on a variety of factors, often relying on assumptions about sender behavior and user preferences. These decisions are influenced by sender reputation, engagement metrics, content quality, list hygiene, IP address reputation, sending frequency, complaint rates, and the completeness of sender information. Providers assume that poor reputation, low engagement, spam-like content, poorly maintained lists, a history of sending spam from an IP address, sudden spikes in sending volume, high complaint rates, and misleading sender information are indicators of unwanted or harmful emails. They also operate under the assumption that users report spam correctly and that they use feedback loops to monitor and address complaints.