143
Server-side email management without encryption (IMAP)
Internet Message Access Protocol
What is port 143?
IMAP on port 143 lets email clients manage messages directly on the server with full multi-device synchronization. Unlike POP3, emails remain on the server and folder structures are maintained. The connection is unencrypted — use IMAPS (port 993) for a TLS-secured connection. IMAP is the foundation of all modern email clients including Outlook, Thunderbird, and mobile apps.
Quick checks
$
nc -zv example.com 143
$
nmap -p 143 example.com
$
telnet example.com 143