# WHATPORT(10025)

## NAME

port 10025 — MTA reinjection (post-filter SMTP) — The stripped-down SMTP listener a content filter reinjects already-scanned mail into.

Protocol: TCP

## DESCRIPTION

Also unregistered with IANA. In the standard amavis setup, master.cf runs a second Postfix smtpd on 127.0.0.1:10025 with most checks disabled, and amavis returns clean mail to it via `$forward_method='smtp:[127.0.0.1]:10025'`. Postfix's own FILTER_README documents the same sandwich with a 10025/10026 pair. A probe sees an ordinary Postfix ESMTP banner, which makes the port easy to mistake for a legitimate public MTA.

## EXPOSURE

**Do not expose.** This listener deliberately runs with relay restrictions and receive overrides removed so that filtered mail passes unchallenged. Reachable from the internet, it is a literal open relay — bind it to the loopback interface.

## CHECK

```sh
printf 'QUIT\r\n' | nc -w 3 127.0.0.1 10025
```

## SEE ALSO

- docs — [Postfix — FILTER_README (SMTP-based content filter port sandwich)](https://www.postfix.org/FILTER_README.html) (postfix.org)
- docs — [amavis — README.postfix (reinjection on 127.0.0.1:10025)](https://www.amavis.org/README.postfix.html) (amavis.org)

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HTML: <https://whatport.net/10025/> · JSON: <https://whatport.net/10025.json> · full dataset: <https://whatport.net/ports.json>