What could potentially reduce the effectiveness of email marketing over time?

The over-saturation of the recipient's inbox plays a significant role in diminishing the effectiveness of email marketing over time. When recipients are inundated with emails from multiple sources, their ability to engage with each individual message declines. They may overlook or disregard emails due to sheer volume, leading to decreased open rates and click-through rates. This phenomenon can lead to email fatigue, where recipients become less responsive to marketing messages, resulting in lower engagement overall.

In contrast, consistent engagement metrics indicate that an audience is still interacting with the content being sent, while infrequent email campaigns may actually help maintain interest rather than diminish it. High levels of customer interaction typically signify a successful campaign, as engaged recipients are more likely to respond positively to marketing efforts. Therefore, overcrowding a recipient's inbox with excessive emails is a primary factor in reducing the effectiveness of email marketing initiatives.