Порт 110 — POP3 (TCP)
What is Port 110?
Протокол поштового офісу 3
This is a well-known port (0–1023) commonly used by core services like POP3. · RFC 1939
When do you need Port 110 open?
Open only if running a mail server where clients retrieve email via POP3. Modern setups prefer IMAP (port 143) or encrypted variants (port 993/995). Close if no mail server is running.
Common uses and software
- Microsoft Outlook
- Mozilla Thunderbird
- Apple Mail
Security
Plain POP3 transmits passwords and email content in clear text. Disable plain POP3 (port 110) and use POP3S (port 995) instead. For multi-device access where messages should remain on the server, switch users to IMAPS (port 993).
Is Port 110 safe?
An open port increases your attack surface. Safety depends on how POP3 is configured.
Keep POP3 up to date with security patches. Require strong authentication and restrict access to the minimum necessary IP addresses.
Test connectivity for Port 110 on any host.
How to Open Port 110
To allow incoming connections to Port 110 (POP3) 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: 110 → Allow the connection → Name and save the rule.
netsh advfirewall firewall add rule name="Open Port 110" dir=in action=allow protocol=tcp localport=110sudo ufw allow 110/tcpsudo iptables -A INPUT -p tcp --dport 110 -j ACCEPTLog into your router (192.168.1.1 or 192.168.0.1) → Port Forwarding → Add a new rule: Protocol TCP, External port 110, Internal IP: your device's local IP, Internal port 110 → Save.
How to close Port 110
If you do not need POP3, block this port in your firewall or router.
To block port 110 on Windows, run the following command in PowerShell or Command Prompt (as Administrator):
netsh advfirewall firewall add rule name="Block Port 110" dir=in action=block protocol=tcp localport=110sudo ufw deny 110/tcpsudo iptables -A INPUT -p tcp --dport 110 -j DROPRemove or disable any port forwarding rule for Port 110.
Frequently Asked Questions
What is Port 110 used for?▾
Port 110 is the default TCP port for POP3. 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 POP3 server — if not, it should remain closed to reduce your attack surface.
Is Port 110 safe to keep open?▾
An open Port 110 increases your attack surface. If you are not actively running POP3, close this port in your firewall and remove any port forwarding rules. If POP3 must be accessible, restrict access to known IP ranges, keep the service software updated with security patches, and use strong authentication.