1. Reduction in Engagement: Emails that are too tailored based on historical data may not resonate with new or evolving customer preferences. 2. Ineffective Campaigns: Strategies that worked in the past might not be effective in the current market, leading to wasted resources. 3. Poor ROI: Overfitted models can lead to lower open rates and click-through rates, ultimately reducing the return on investment (ROI) for email campaigns.