# WHATPORT(110)

## NAME

port 110 — POP3 — POP3 — download-and-usually-delete mail retrieval, with no server-side folder state.

Protocol: TCP  
IANA registry

## DESCRIPTION

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.

## EXPOSURE

**Expose with care.** Only expose 110 when the server requires STLS before accepting credentials; otherwise use POP3S on 995.

## CHECK

```sh
printf 'CAPA\r\nQUIT\r\n' | nc -v MAIL_HOST 110
```

## SEE ALSO

- spec — [RFC 1939 — Post Office Protocol Version 3](https://www.rfc-editor.org/rfc/rfc1939.html) (rfc-editor.org)
- source — [Dovecot (IMAP/POP3 server) source repository](https://github.com/dovecot/core) (github.com)
- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/110/> · JSON: <https://whatport.net/110.json> · full dataset: <https://whatport.net/ports.json>