# WHATPORT(24)

## NAME

port 24 — Any private mail system — Registered to IANA as "any private mail system" — a deliberately open-ended slot, not a specific protocol.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA's entry for port 24 is literally 'any private mail system', assigned to Rick Adams, meaning the number was set aside for private mail transports rather than any one named protocol. There is no RFC and no reference implementation. In practice almost nothing binds it, and when it appears on a scan it is usually a bespoke or legacy mail relay rather than a standard MTA. Standard mail lives on 25, 465, 587 and 993 instead.

## EXPOSURE

**Expose with care.** No defined protocol means no defined security properties; if a private mail transport is really listening here, assume cleartext until proven otherwise.

## CHECK

```sh
nc -vz TARGET 24
```

## SEE ALSO

- 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/24/> · JSON: <https://whatport.net/24.json> · full dataset: <https://whatport.net/ports.json>