Port 587 is used by SMTP with STARTTLS (SMTP/TLS). The modern standard port for email submission. Email clients (Outlook, Thunderbird, Apple Mail) should use port 587 with STARTTLS to send email.
What Does an Open Port 587 Mean?
A mail server is accepting email submissions from authenticated users. The recommended port for email client configuration.
This port should NOT be open to the public internet on typical systems. If you see it open, investigate immediately.
Security Risk Level
Low Risk
How to Check if Port 587 Is Open
Use the ExamineIP Port Scanner to check if port 587 is open on any IP address from the public internet. Enter the target IP and select the relevant port preset.
How to Close Port 587
- Stop the service using port 587 if you no longer need it
- Add a firewall rule blocking inbound connections on port 587
- Check your router for port forwarding rules that expose this port
- Run
netstat -ano | findstr :587(Windows) to see which process is using it
Related Ports
SMTP/TLS is related to: {implode(‘, ‘, Array)}
Protect Your Open Ports
If you need services like remote access, use a VPN to create a private encrypted tunnel instead of exposing ports directly to the internet. A VPN also hides your real IP address so port scanners cannot identify your device. Try PureVPN or IPVanish.