What is the default port number used by the SMTP protocol?

The default port number used by the SMTP (Simple Mail Transfer Protocol) is 25. SMTP is primarily used for sending emails between servers and for sending emails from a client to a server. Port 25 is the traditionally assigned port for SMTP traffic, allowing email servers to communicate with each other and enabling email transmission across the Internet.

Understanding port assignments is crucial for configuring network services, as it helps ensure proper communication for various protocols. The other ports listed serve different functions: Port 80 is used for HTTP traffic (web browsing), Port 443 is designated for HTTPS traffic (secure web browsing), and Port 8080 is commonly used for alternative HTTP services and proxy servers. Therefore, recognizing that SMTP utilizes port 25 is essential for properly setting up email services and diagnosing potential issues related to email transmission.