110
Download email from server without encryption (POP3)
Post Office Protocol v3
What is port 110?
POP3 on port 110 allows email clients to download messages from a mail server. Unlike IMAP, POP3 typically downloads and deletes messages from the server, with no synchronization across multiple devices. The connection is entirely unencrypted, exposing credentials and message content. It has been superseded by POP3S (port 995) and IMAP/IMAPS for modern use.
Quick checks
$
nc -zv example.com 110
$
nmap -p 110 example.com
$
telnet example.com 110