Standard SMTP port?

The standard port for the SMTP protocol is 25.

However, for secure email transmission, ports are often used:

• 465 — for SMTP with SSL/TLS (SMTPS)
• 587 — for SMTP with STARTTLS (recommended port for email clients to send mail)

Example of setting up email sending via SMTP on port 25:

# Example telnet session to SMTP server on port 25
telnet smtp.example.com 25