Different SMTP ports serve different purposes and security levels. Choosing the right port is essential for reliable email delivery.
Port 25 - Traditional SMTP
Port 25 is the original SMTP port, primarily used for server-to-server communication. Many ISPs block this port for security reasons.
Port 587 - Submission Port (Recommended)
Port 587 is the standard for email submission with authentication. It supports STARTTLS encryption and is widely supported.
Port 465 - SMTPS (Legacy SSL)
Port 465 uses implicit SSL/TLS encryption. While secure, it's considered legacy. Port 587 with STARTTLS is preferred.
Port 2525 - Alternative Submission
Port 2525 is an alternative to 587, useful when ISPs block standard ports. Supports the same features as port 587.
Pro Tips
- Use port 587 with STARTTLS for most email clients
- Port 465 is acceptable if 587 is blocked
- Avoid port 25 for email client configuration
- Test connectivity if emails aren't sending