SMTP Relay
An SMTP relay is a mail server or service that forwards email messages between different email servers or domains, acting as an intermediary in the email delivery process. It ensures reliable transmission by handling authentication, routing, and delivery to the recipient's mail server, often used to improve deliverability and manage outbound email traffic.
Developers should learn and use SMTP relays when building applications that send transactional or marketing emails, as they provide better deliverability, scalability, and security compared to direct sending from application servers. They are essential for handling high email volumes, implementing authentication protocols like SPF and DKIM, and integrating with email service providers in cloud-based or on-premises environments.