Should port 110 be open to the internet?

Should not be public. Unencrypted. Use POP3S (995) or, better, IMAP over TLS (993).

Should not be public

Port 110 — POP3

Legacy mail retrieval that downloads messages to one device.

Port

110

Service

POP3

Protocol

TCP

Security guidance

Unencrypted. Use POP3S (995) or, better, IMAP over TLS (993).

Test port 110 yourself

From your own machine, against any host (swap in your domain):

macOS / Linux — netcat

nc -vz example.com 110

Any OS — nmap

nmap -p 110 example.com

Windows — PowerShell

Test-NetConnection example.com -Port 110

open = a service answered on port 110; closed = the host replied but nothing is listening; filtered = a firewall silently dropped the probe. These test from your network — our port checker tests from the outside, the view that matters for security.

Is port 110 open on your server?

Test it from outside your network — the only view that matters.

Check port 110

Other common ports

20 · FTP data 21 · FTP control 22 · SSH / SFTP 23 · Telnet 25 · SMTP 53 · DNS 80 · HTTP 123 · NTP 143 · IMAP 161 · SNMP 389 · LDAP 443 · HTTPS 445 · SMB 465 · SMTPS 587 · SMTP submission 993 · IMAPS 995 · POP3S 1433 · Microsoft SQL Server 1521 · Oracle Database 2082 · cPanel 2083 · cPanel (TLS) 3000 · Node.js / dev server 3306 · MySQL / MariaDB 3389 · RDP 5432 · PostgreSQL 5900 · VNC 6379 · Redis 8080 · HTTP alternate 8443 · HTTPS alternate 9200 · Elasticsearch 27017 · MongoDB