SMTP (Simple Mail Transfer Protocol) ports are communication endpoints that enable email transmission between servers and clients. When you send an email, your email client or server connects to an SMTP server using a specific port number to deliver your message. Different ports are used based on security requirements and server configurations.

The most common SMTP ports are:

• Port 25: The original SMTP port for server-to-server email relaying. Most ISPs block this port for outgoing mail to prevent spam.
• Port 587: The standard port for email submission from email clients to mail servers. It requires authentication and supports TLS encryption.
• Port 465: Originally designated for SMTPS (SMTP over SSL), this port uses implicit SSL/TLS encryption. While deprecated, some services still use it.
• Port 2525: An alternative port when standard ports are blocked, often supporting TLS encryption.

For most users sending emails through hosting services, port 587 with STARTTLS is recommended as it provides secure transmission while maintaining compatibility. Always check your hosting provider's documentation for their specific SMTP port requirements, as using the wrong port can prevent email delivery. Proper port configuration ensures your emails reach their destination securely and reliably.