Route outing SMTP traffing through a non-standard port to anotherqmail server

I am sure this has come up before, but I couldn't find anything with a
cursory search of Google. Here's my problem:

I recently moved to Chicago where RCN is available (cable modem).

I use my own mail server (qmail) located within my private LAN (behind
NAT) on RCN.

I found out that RCN doesn't seem to allow outgoing traffic on port 25;
probably because of spammers and I can somewhat understand this. I do
have an option of using the RCN mail servers (which aren't the greatest
or most reliable as is with most cable-company mail-servers).

I do have a machine running qmail sitting at a friend's ISP in their
colo. It's running linux and the latest qmail. Is there a way I can
route mail from my mail client (currently Mozilla Thunderbird) to this
external qmail server on a different port? I am sure there is, but I am
not sure what I would need to configure on the qmail side?

The machine sitting at the colo is running a basic iptables firewall
that allows port 25 and a few other services. Is this where some "port
translation" would be done?

Thanks for any help or pointers to help,

Tim

Tim Mavers wrote:
<snip>
> I found out that RCN doesn't seem to allow outgoing traffic on port 25;
Very common these days.

> probably because of spammers and I can somewhat understand this. I do
> have an option of using the RCN mail servers (which aren't the greatest
> or most reliable as is with most cable-company mail-servers).
OK.

> I do have a machine running qmail sitting at a friend's ISP in their
> colo. It's running linux and the latest qmail. Is there a way I can
> route mail from my mail client (currently Mozilla Thunderbird) to this
> external qmail server on a different port? I am sure there is, but I am
> not sure what I would need to configure on the qmail side?
This part is trivial. I put directions below, but man qmail-remote for
more info.

> The machine sitting at the colo is running a basic iptables firewall
> that allows port 25 and a few other services. Is this where some "port
> translation" would be done?
This is the tricky part.

One way to do this would be to create a second instance of qmail on your
friend's box. To do this, simply edit the conf-qmail file in the qmail
source directory and change /var/qmail to something like /var/qmail2.
Then configure tcpserver to run the qmail-smtpd script on s different
port, like 2500. You'd have to put your IP address in his tcp.smtp file
to allow relaying. Make sure you put something in the control/rcpthosts
file, so you won't be an open relay.

Then, on your box, simply create a control/smtproutes file, and
populate it with the following:

:[your.friend's.ip.address]:2500

Don't be tempted to just run a second tcpserver on a different port and
use the same qmail queue - you run the risk of name collisions.

This may seem like a lot of work, and someone else may have a better
suggestion. If not, you can try it out. Good luck.

Tim Mavers wrote:
> I am sure this has come up before, but I couldn't find anything with a
> cursory search of Google. Here's my problem:
>
> I recently moved to Chicago where RCN is available (cable modem).
>
> I use my own mail server (qmail) located within my private LAN (behind
> NAT) on RCN.
>
> I found out that RCN doesn't seem to allow outgoing traffic on port 25;
> probably because of spammers and I can somewhat understand this. I do
> have an option of using the RCN mail servers (which aren't the greatest
> or most reliable as is with most cable-company mail-servers).
>
> I do have a machine running qmail sitting at a friend's ISP in their
> colo. It's running linux and the latest qmail. Is there a way I can
> route mail from my mail client (currently Mozilla Thunderbird) to this
> external qmail server on a different port? I am sure there is, but I am
> not sure what I would need to configure on the qmail side?

On your qmail box:
/var/qmail/control/smtproutes
:your.mates.box:2500

This will make qmail relay to your friends machine on port 2500. Get
mozilla to deliver to port 25 on your qmail server.

> The machine sitting at the colo is running a basic iptables firewall
> that allows port 25 and a few other services. Is this where some "port
> translation" would be done?

Yeah, Just redirect port 2500 to the target 25. The exact runes escape
me for now (I'm more familiar with Ipchains).

> Thanks for any help or pointers to help,
>
> Tim


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