A standard cause for this is firewall software on the internal machine.
From: Chris Buechler [mailto:cbuechler at gmail dot com]
Sent: Thursday, 28 July 2005 11:52 a.m.
Cc: m0n0wall at lists dot m0n0 dot ch
Subject: Re: [m0n0wall] Inbound NAT doesn't working!
On 7/27/05, TrueAlex <truealex at nsmu dot ru> wrote:
> I'm using generic-PC monowall version 1.2b7 on Pentium MMX with 2
> network cards. I just want to map external 25 port to my internal mail
> server. I've done all setup by manual, strongly checks all other
> "related stuffs" such as filtration on ISP side and other common
> mistakes; trying to use another ports and servers. and nothing. I also
> turn on packets logging for NAT rule and seen that packets is PASSED
> (by logs) thru monowall, but I don't find any of them on my mail
> server. Then I just setup inbound NAT on my Windows machine and it
> works fine! So, my conclusion is: monowall have a bug.
and you would conclude wrong. no NAT issues in 1.2b7.
can that server get to the internet just fine? uses your m0n0wall as its
default gateway? you sure the packets aren't getting there, as it sounds
like they are? run tcpdump or ethereal or some sniffer on the server to