POP3 — download-and-usually-delete mail retrieval, with no server-side folder state.
A client connects, authenticates with USER/PASS or APOP, lists messages by number, retrieves them with RETR, and typically marks them deleted; the mailbox is a flat list with no folders and no cross-device sync. Port 110 is the cleartext port, upgraded in practice with STLS or replaced by implicit-TLS POP3S on 995. It is still served by Dovecot and by most hosting providers for legacy clients and scripted fetchers. Its appearance on a scan usually means an old mail host or a shared-hosting control panel.
Expose with care
Only expose 110 when the server requires STLS before accepting credentials; otherwise use POP3S on 995.
$ printf 'CAPA\r\nQUIT\r\n' | nc -v MAIL_HOST 110Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.