PORT 110 / TCPEmail & MessagingExposure Risk: Medium

Port 110: POP3 — Post Office Protocol v3 (Unencrypted)

Used by email clients to retrieve messages from a mail server. Superseded by encrypted POP3S on Port 995.

Default Service

POP3

Process: dovecot

Transport Protocol

TCP

IANA Registered Port 110

Docker Port Flag

-p 110:110

Container to Host Mapping

How to Check & Kill Process on Port 110 (EADDRINUSE Fix)

macOS & Linux (lsof / kill)

# Find process using port 110
sudo lsof -i :110

# Instantly kill process on port 110
lsof -ti:110 | xargs kill -9

Windows (PowerShell & CMD)

# Find PID listening on port 110
netstat -ano | findstr :110

# Force kill by PID
taskkill /PID <PID_NUMBER> /F

Cross-Platform Node.js One-Liner

# Kill port 110 via npx
npx kill-port 110

# Or diagnose via Castov CLI
npx castov fix "EADDRINUSE :::110"

Linux Firewall (UFW) & Connectivity Test

# Test if port 110 is reachable
nc -zv localhost 110

# Allow or deny port 110 in UFW
sudo ufw allow 110/tcp

Frequently Asked Questions about Port 110

What is Port 110 used for?

Port 110 is the standard network port for POP3 (Post Office Protocol v3 (Unencrypted)) operating over TCP. The typical system daemon or process is dovecot.

How do I kill a process running on Port 110 (EADDRINUSE)?

On macOS and Linux, run: lsof -ti:110 | xargs kill -9 (or npx kill-port 110). On Windows PowerShell/CMD, run: netstat -ano | findstr :110 and then taskkill /PID <PID> /F.

Is it safe to expose Port 110 to the internet?

Port 110 has a Medium security risk profile. Used by email clients to retrieve messages from a mail server. Superseded by encrypted POP3S on Port 995.