Integration with Postfix (NNCP)

Integration with Postfix

This section is taken from Postfix and UUCP manual and just replaces UUCP-related calls with NNCP ones.

Setting up a Postfix Internet to NNCP gateway

Here is how to set up a machine that sits on the Internet and that forwards mail to a LAN that is connected via NNCP.

You need an nncp-exec program that extracts the sender address from mail that arrives via NNCP, and that feeds the mail into the Postfix sendmail command.
Define a pipe(8) based mail delivery transport for delivery via NNCP:
```
/usr/local/etc/postfix/master.cf:
nncp      unix  -       n       n       -       -       pipe
  flags=Rqhu user=nncp argv=nncp-exec -quiet $nexthop sendmail $recipient
```
This runs the nncp-exec command to place outgoing mail into the NNCP queue after replacing $nexthop by the receiving NNCP node and after replacing $recipient by the recipients. The pipe(8) delivery agent executes the nncp-exec command without assistance from the shell, so there are no problems with shell meta characters in command-line parameters.

Pay attention to flags, containing R, telling Postfix to include Return-Path: header. Otherwise that envelope sender information may be lost. Possibly you will also need somehow to preserve that header on the receiving side, because sendmail command will replace it. For example you can rename it before feeding to sendmail with reformail -R Return-Path: X-Original-Return-Path: | sendmail, or extract with:
```
#!/bin/sh -e

tmp=`mktemp`
trap "rm -f $tmp" HUP PIPE INT QUIT TERM EXIT
cat > $tmp
sendmail -f "`reformail -x Return-Path: < $tmp`" $@ < $tmp
```
Also pay attention that maildrop does not like From_ mbox-style header, so you possibly want:
```
mailbox_command = reformail -f0 | maildrop -d ${USER}
```
Specify that mail for example.com, should be delivered via NNCP, to a host named nncp-host:
```
/usr/local/etc/postfix/transport:
    example.com     nncp:nncp-host
    .example.com    nncp:nncp-host
```
See the transport(5) manual page for more details.
Execute the command postmap /etc/postfix/transport whenever you change the transport file.

Enable transport table lookups:

/usr/local/etc/postfix/main.cf:
    transport_maps = hash:$config_directory/transport

Add example.com to the list of domains that your site is willing to relay mail for.
```
/usr/local/etc/postfix/main.cf:
    relay_domains = example.com …other relay domains…
```
See the relay_domains configuration parameter description for details.
Execute the command postfix reload to make the changes effective.

Setting up a Postfix LAN to NNCP gateway

Here is how to relay mail from a LAN via NNCP to the Internet.

You need an nncp-exec program that extracts the sender address from mail that arrives via NNCP, and that feeds the mail into the Postfix sendmail command.
Specify that all remote mail must be sent via the nncp mail transport to your NNCP gateway host, say, nncp-gateway:
```
/usr/local/etc/postfix/main.cf:
    relayhost = nncp-gateway
    default_transport = nncp
```
Postfix 2.0 and later also allows the following more succinct form:
```
/usr/local/etc/postfix/main.cf:
    default_transport = nncp:nncp-gateway
```
Define a pipe(8) based message delivery transport for mail delivery via NNCP:
```
/usr/local/etc/postfix/master.cf:
nncp      unix  -       n       n       -       -       pipe
  flags=Fqhu user=nncp argv=nncp-exec -quiet $nexthop sendmail $recipient
```
This runs the nncp-exec command to place outgoing mail into the NNCP queue. It substitutes the hostname (nncp-gateway, or whatever you specified) and the recipients before execution of the command. The nncp-exec command is executed without assistance from the shell, so there are no problems with shell meta characters.
Execute the command postfix reload to make the changes effective.