How do ESPs queue and retry messages?

Essential ESP features start with reliable deliverability infrastructure: proper authentication support, reputation monitoring, bounce handling, and feedback loop processing. The best features mean nothing if your emails don't reach inboxes. Ask potential ESPs about their delivery rates, how they handle reputation issues, and whether they offer dedicated IPs for larger senders.

Campaign management capabilities should match your operational needs. Consider template builders, dynamic content support, A/B testing, segmentation tools, automation workflows, and personalization options. If your team lacks design resources, visual editors matter more. If you run complex automated journeys, evaluate workflow builders carefully. Integration with your CRM, e-commerce platform, and other tools often proves essential.

Don't overlook analytics, compliance features, and support quality. Robust reporting helps you improve performance over time. Built-in consent management, suppression list handling, and preference centers simplify compliance. Responsive support becomes critical when you face urgent delivery problems or technical issues. Also consider pricing structure, contract flexibility, and how costs scale with your growth. The best ESP for you matches your current needs while providing room to grow into more sophisticated email marketing.