SMTPrelay

SMTPrelay refers to the process where an email server forwards an email message to another mail server for delivery. This is a fundamental part of how the Simple Mail Transfer Protocol (SMTP) works. When an email is sent from a client (like an email program) to a server, that server typically doesn't directly deliver it to the recipient's mailbox. Instead, it acts as a relay, using DNS (Domain Name System) to find the mail server responsible for the recipient's domain.

Once the originating server identifies the destination mail server, it establishes a connection and transfers the email to it. This process can involve multiple hops if the recipient's mail server is not directly reachable or if there are intermediate servers involved in the mail flow. For instance, a company might use an outgoing SMTP relay service to manage its email sending, ensuring compliance, security, and reliable delivery. These services act as a central point for all outbound emails from an organization.

SMTP relay is crucial for the global email infrastructure, enabling seamless communication between different email providers and networks. Without this relay mechanism, email delivery would be significantly more complex and less efficient. It allows for separation of concerns, where one server handles sending and another handles receiving, optimizing the process for scalability and management. Misconfigurations in SMTP relay settings can lead to emails being rejected or failing to be delivered.