An Email Service Provider (ESP) is a service organization that provides transactional and/or marketing email services.
Most ESPs include features that allow customers to:
ESPs like SendGrid also provide expertise on increasing your email deliverability, preserving your sending reputation. They may utilize features and tools to accomplish this, such as:
An ESP may provide email services via a user interface (UI), or may also be an SMTP provider. SendGrid provides both services.