Which protocol uses port number 25?

Port number 25 is designated for the Simple Mail Transfer Protocol (SMTP), which is commonly used for sending emails across the Internet. SMTP serves as a communication protocol for email transmission, facilitating the transfer of messages from client to server and between servers.

Understanding the context of its use is crucial. SMTP operates as a push protocol, allowing users to send messages from their email clients to their respective mail servers. From there, the messages can be transmitted to the recipient's mail server, ensuring that email delivery is managed efficiently.

This designation contrasts with the other protocols mentioned. For example, FTP (File Transfer Protocol) primarily utilizes port numbers 20 and 21 for transferring files, while HTTP (Hypertext Transfer Protocol) operates on port 80, which is essential for web traffic. HTTPS (HTTP Secure) encrypts web traffic and typically uses port 443. Therefore, the clear association of port 25 with SMTP distinguishes it within the context of email services.