Port 465 — SMTPS (TCP)
What is Port 465?
Sikker SMTP
This is a well-known port (0–1023) commonly used by core services like SMTPS. · RFC 8314
When do you need Port 465 open?
Open on mail submission servers accepting client email via implicit TLS. Needed if users send email through your mail server. Port 587 (STARTTLS) is the modern preferred alternative.
Common uses and software
- Postfix (implicit TLS)
- Gmail SMTP relay
- Microsoft 365 SMTP relay
- SendGrid
- Mailgun
Security
Port 465 with implicit TLS is inherently more secure than STARTTLS on port 587 because TLS is mandatory from connection start — there is no plain-text upgrade handshake that can be intercepted. Ensure valid TLS certificates and strong cipher suites. Authentication is required; never allow unauthenticated relay.
Is Port 465 safe?
An open port increases your attack surface. Safety depends on how SMTPS is configured.
Keep SMTPS up to date with security patches. Require strong authentication and restrict access to the minimum necessary IP addresses.
Test connectivity for Port 465 on any host.
How to Open Port 465
To allow incoming connections to Port 465 (SMTPS) from outside your network, configure your firewall and add a port forwarding rule on your router pointing to your device's local IP address.
Open Windows Defender Firewall → Advanced Settings → Inbound Rules → New Rule → Port → TCP → Specific local ports: 465 → Allow the connection → Name and save the rule.
netsh advfirewall firewall add rule name="Open Port 465" dir=in action=allow protocol=tcp localport=465sudo ufw allow 465/tcpsudo iptables -A INPUT -p tcp --dport 465 -j ACCEPTLog into your router (192.168.1.1 or 192.168.0.1) → Port Forwarding → Add a new rule: Protocol TCP, External port 465, Internal IP: your device's local IP, Internal port 465 → Save.
How to close Port 465
If you do not need SMTPS, block this port in your firewall or router.
To block port 465 on Windows, run the following command in PowerShell or Command Prompt (as Administrator):
netsh advfirewall firewall add rule name="Block Port 465" dir=in action=block protocol=tcp localport=465sudo ufw deny 465/tcpsudo iptables -A INPUT -p tcp --dport 465 -j DROPRemove or disable any port forwarding rule for Port 465.
Frequently Asked Questions
What is Port 465 used for?▾
Port 465 is the default TCP port for SMTPS. It is used by servers and applications that need to accept incoming connections for this service. Whether you need it open depends on whether you are actively running a SMTPS server — if not, it should remain closed to reduce your attack surface.
Is Port 465 safe to keep open?▾
An open Port 465 increases your attack surface. If you are not actively running SMTPS, close this port in your firewall and remove any port forwarding rules. If SMTPS must be accessible, restrict access to known IP ranges, keep the service software updated with security patches, and use strong authentication.