Port 110 — POP3
Quick reference for TCP/UDP port 110, used by POP3. Includes what the service does, security guidance and related ports.
What is port 110?
Post Office Protocol v3 for retrieving email.
What port does POP3 use?
POP3 listens on port 110 by default.
Is port 110 open? How to check
Run one of these from your computer, replacing HOST with the IP address or domain you want to test.
nc -zv HOST 110
Test-NetConnection HOST -Port 110
nmap -p 110 HOST
A refused or timed-out connection means the port is closed or filtered by a firewall.
Security guidance
High risk — do not expose to the internet
Port 110 (POP3) is high-risk because the service it carries is a frequent target for credential attacks, brute force or unpatched-vulnerability scanning. Keep it bound to localhost or your VPN, never forward it directly on a router, and require strong authentication.
Related ports
Frequently asked
What is port 110 used for?+
Port 110 is the standard TCP/UDP port for POP3. Post Office Protocol v3 for retrieving email.
What port does POP3 use?+
POP3 listens on port 110 by default.
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