What is the port number for SMTP?

SMTP = port 25 (TCP).

SMTP = Port 25 (TCP)

SMTP (Simple Mail Transfer Protocol) is used to send email between mail servers.

Memory tip: "25 = Send Mail To People"

Related ports:

• Port 587: SMTP with authentication (submission)
• Port 465: SMTPS (deprecated but still used)

Go deeper:

• Simple Mail Transfer Protocol — Wikipedia overview confirming TCP port 25 for mail relay between servers.
• List of TCP and UDP port numbers — the broader lookup table placing 25 among the well-known ports.