SMTP Port Checker

Check SMTP port availability for any hostname. Verify DNS resolution and see which standard email ports are available for your mail server.

Which SMTP port should you use?

Port 587 (Submission) is the recommended port for sending email from email clients and applications. It uses STARTTLS to upgrade the connection to TLS encryption and requires authentication. This is the port you should use in most cases.

Port 465 (SMTPS) uses implicit TLS — the connection is encrypted from the start. Originally deprecated, it was re-standardized in RFC 8314 (2018). Some providers prefer it over port 587.

Port 25 (SMTP) is used for server-to-server email relay. It's how mail servers deliver messages to each other. Most residential ISPs block outbound port 25 to prevent spam. You generally should not use port 25 for sending email from applications.

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