SMTP server or "forwarding"?

[Jonathan Berry]

On 8/27/05, Les Mikesell <lesmikesell at gmail.com> wrote:
> On Sat, 2005-08-27 at 00:11, Jonathan Berry wrote:
> 
> > Okay, a lot of ISPs now block port 25 out to anything other than their
> > SMTP server.  In some situations, it would be nice to circumvent this
> > to get to another SMTP server if one is not available.
> 
> If your ISP can't keep their mail server running, find another ISP.

Actually, I mean not available as in not there, rather than not
functional at times.  And switching ISPs is not an option for someone
on a University network (see other emails).

> > So what I had
> > though is to setup my FC4 linux box to listen for SMTP traffic on a
> > non-standard port.
> 
> How is anything else going to know to send to the non-standard port?

It won't.  I only care about mail clients being able to connect to it,
and I can set them up that way.

> If you are have multiple clients on a local LAN, you can have your
> own mail server working on port 25 for local clients that won't be
> blocked by the ISP, and configure this server to forward through
> the ISP's server.

Right.  But the client I want to connect to it is not on the local
LAN.  It needs to come across the internet.

> > Actually, I could just have my hardware router
> > forward whatever port to 25 on the computer, so the non-standard port
> > part should be easy.  It would be nice to have a workable solution
> > with as little as possible.  Does anyone know of some way that I could
> > maybe take any traffic to my server on my chosen high port and forward
> > it along to my ISP's SMTP server on port 25?  It sounds possible, but
> > sketchy enough to where it might not be.  Any ideas?
> 
> It is easy to do this either with iptables or xinetd's 'redirect'
> function, but I don't see the point here.  If you have one email
> client, point it to the ISP.  If you want a local server, use
> its smart_host feature to send everything outbound through the ISP.
> 
> --
>  Les Mikesell

Obviously, I was not very clear on what I wanted to do.  Sorry about
that.  Your two choices do not describe what I want.  So can iptables
or the xinetd redirect take traffic and send it back out the same
interface to my ISP's SMTP server?  That sounds like what I might want
if so.

Jonathan