Port 110: POP3
Port 110 is POP3, which downloads mail to one device and by default deletes it from the server. It is unencrypted; the encrypted equivalent is POP3S on port 995.
| Port number | 110 |
|---|---|
| Service | Post Office Protocol v3 |
| Protocol | TCP |
| Category | |
| Default encryption | No |
| IANA service name | pop3 |
| IANA transports | TCP, UDP |
| Used in practice | TCP |
Which ports are related to port 110?
The port a reader usually needs next is the encrypted or plaintext twin of this one, so those are listed first rather than buried in a generic list.
What commonly listens on port 110?
- Dovecot and Courier on Linux mail servers
- Legacy hosting control panels offering POP3 access
How do I check whether port 110 is open?
Port 110 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 110 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 110 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':110 ' | Lists the process bound to port 110 on Linux. On macOS use lsof -nP -iTCP:110 -sTCP:LISTEN, on Windows netstat -ano | findstr :110 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is the difference between port 110 and port 995?
Port 110 is plain POP3, where the login and every message travel in clear text. Port 995 is POP3S, the same protocol wrapped in TLS from the moment the connection opens. Use 995; RFC 8314 treats cleartext mail access as obsolete.
Should I use POP3 on port 110 or IMAP?
IMAP, in almost every case. POP3 downloads mail to a single device and deletes the server copy by default, which loses your mail if that device fails and makes multi-device access impractical. IMAP on port 143, or IMAPS on 993, keeps the mailbox on the server.
What is port 110 used for?
Port 110 is POP3, which downloads mail to one device and by default deletes it from the server. It is unencrypted; the encrypted equivalent is POP3S on port 995.
Is port 110 TCP or UDP?
IANA assigns port 110 on TCP, UDP. In practice it carries TCP. The UDP registration is historical and unused.
Is port 110 secure?
Port 110 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 110 on my firewall?
Only if you specifically need POP3. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.