What is the central function of an SMTP queue?

The central function of an SMTP queue is to temporarily store emails before they are sent to their recipients. When an email is generated and sent, it does not always reach the recipient's server immediately due to various reasons, such as server unavailability, network issues, or high traffic. The SMTP queue acts as a holding area for these emails, ensuring they are processed in the correct order and that delivery attempts are made when the recipient's server becomes available. This queuing mechanism is crucial for maintaining reliable email communication, as it helps manage the flow of messages despite potential obstacles in the sending and receiving process.