What port number is associated with the SMTP protocol?

The Simple Mail Transfer Protocol (SMTP) is primarily used for sending emails across networks. It operates using TCP (Transmission Control Protocol) and is predominantly associated with port number 25. This port is the default used for SMTP communication, facilitating the transfer of email messages between servers and allowing email clients to send out messages.

While other ports listed serve different protocols—such as port 80, which is for HTTP (HyperText Transfer Protocol), port 443 for HTTPS (HTTP Secure), and port 110 for POP3 (Post Office Protocol version 3 used for receiving emails)—none of these ports are used for sending emails via the SMTP protocol. Understanding the specific functions of these ports is crucial, as it highlights the unique roles they play in network communications, particularly within the context of email services.