ESP
Email service provider: software for sending, templating, and often automating email.
Definition
An ESP (email service provider) is a platform that handles email creation, list or audience management, sending infrastructure, and usually analytics. Some ESPs focus on marketing campaigns, others on transactional APIs, and a newer class is AI-native.
Why it matters
Choosing an ESP shapes your deliverability posture, automation model, and whether agents can operate email programmatically.