srl
POP3
Post Office Protocol version 3 (POP3) is a mail retrieval protocol: a client connects to the mail server, authenticates, and downloads messages to the local machine. Unlike IMAP, POP3 is a single-mailbox, download-and-store protocol — it does not synchronise folders, flags, or server-side state.
Default ports:
Port Service Encryption 110 POP3 Plaintext — STARTTLS optional 995 POP3S Implicit TLS 110 POP3 + STLS STARTTLS upgrade 2025–2026 context: POP3 is legacy, and that is the entire security story. It is still deployed on mail appliances, cPanel/Plesk hosting, and industrial equipment because it is simple — and it is frequently exposed to the internet without rate limiting, with plaintext credentials on port 110, and with no MFA. The current attack surface is not the protocol itself but the mail server implementation (Dovecot, Courier, Cyrus, Exim, Postfix), where 2025–2026 produced a steady stream of CVEs in mail parsers, TLS handling, and authentication.