Port 25 — SMTP

TCP · Port 25/TCP is used for the Simple Mail Transfer Protocol (SMTP), a standard protocol for sending and receiving email. SMTP plays a crucial role in network security, as it enables secure communication between mail servers and helps prevent spam and phishing attacks.

Port Number: 25
Service Name: SMTP
Protocol: TCP
Common Software: Postfix, Exim, Sendmail

Security Notes

Should only accept connections from authenticated senders. Open relays are exploited for spam.

FAQ

What is port 25 used for?

Port 25 is used for SMTP. Port 25/TCP is used for the Simple Mail Transfer Protocol (SMTP), a standard protocol for sending and receiving email. SMTP plays a crucial role in network security, as it enables secure communication between mail servers and helps prevent spam and phishing attacks. Common software: Postfix, Exim, Sendmail.

Is port 25 dangerous to leave open?

Should only accept connections from authenticated senders. Open relays are exploited for spam.

How do I check if port 25 is open?

Use nmap: nmap -p 25 <target> or check locally: ss -tlnp | rg 25