1. Features and Integrations: Look for an ESP that offers the features you need, such as automation, segmentation, and A/B testing. Ensure it can integrate with your existing CRM and other tools. 2. Pricing: Compare the cost structures of different ESPs to find one that fits your budget. Some providers offer pay-as-you-go plans, while others have monthly or annual subscriptions. 3. User Experience: A user-friendly interface can save you time and reduce the learning curve. Opt for an ESP that offers a straightforward and intuitive platform. 4. Customer Support: Reliable customer support is crucial. Check if the ESP offers 24/7 support, live chat, and comprehensive documentation. 5. Reputation and Reviews: Research the provider's reputation by reading reviews and case studies. Look for feedback on their service quality and reliability.