Several factors can influence the fees charged by ESPs:
List Size: The number of subscribers in your email list is a significant factor. Larger lists generally incur higher costs. Email Volume: The number of emails sent each month also affects the cost. Higher volumes may require more resources and thus higher fees. Features: Advanced features like A/B testing, automation, and advanced analytics may come at an additional cost. Support Level: Access to dedicated customer support or a personal account manager may increase fees.