What port number is commonly associated with SMTP?

The port number commonly associated with SMTP, or Simple Mail Transfer Protocol, is 25. This protocol is primarily used for sending emails across networks. When an email is sent from one server to another, it typically uses port 25 to establish this communication.

Port 25 is designated for SMTP in the original specifications of the protocol. While there are other ports associated with email, such as port 587 for SMTP with STARTTLS (secure transmission) or port 465 (which was never formally recognized but is used for SMTP over SSL), port 25 remains the standard for unencrypted email transmission between servers.

The other listed port numbers serve different protocols and purposes: port 80 is used for HTTP traffic, facilitating web browsing; port 443 handles HTTPS traffic, which is secure web browsing; and port 8080 is often used as an alternative HTTP port for web servers. Understanding these port assignments is key to grasping how different services communicate over the internet.