SMTP server or "forwarding"?

[Jonathan Berry]

On 8/27/05, Alexander Dalloz <ad+lists at uni-x.org> wrote:
> Am Sa, den 27.08.2005 schrieb Jonathan Berry um 7:11:
> 
> > 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.  So what I had
> > though is to setup my FC4 linux box to listen for SMTP traffic on a
> > non-standard port.  Actually, I could just have my hardware router
> 
> Client port and daemon port are not the same, as they are for different
> transmission directions. So if the ISP blocks outgoing port 25, why
> letting the MTA listen on a non-standard port for incoming connections?

I don't quite follow you here.  To send mail to an SMTP, I (the
client) normally connect to port 25, right?  I think I explained what
I want better in the email I just sent.

> > 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
> 
> Other MTAs do not know of any non-standard ports you may use. There is
> no "trick" to make them know what you may expect.

Yes, I know.  I only want *my* MTA to listen on the non-standard port.
 Then it would talk to my ISP's server on port 25 like it expects.

> > sketchy enough to where it might not be.  Any ideas?  I figure I could
> > always just setup my own SMTP server and that should work.  But I
> > would need to make sure I did that right as I do not want to aid in
> > the spread of spam and/or viruses.  Since it would be on a strange
> > port, it shouldn't be as big a problem, if at all.  Any ideas on that
> > point?  So, what do you think of my idea and options?  If I were to go
> > the route of setting up my own SMTP server (perhaps even so far as a
> > whole email server) any tips as to where to start looking for info on
> > doing this right?
> 
> I do not really understand your aim. If your ISP blocks outgoing port
> 25, then he does for good reasons. He on the other side offers you to
> send mail using his mail exchanger as a smart host. That is a standard

I explained better in my last email.  I'm dealing with a University,
not a normal ISP.  Unfortunately, as far as I know, there is no
accessible SMTP server.  Otherwise, I would just point the mail client
at that and be done with it.

> practise. If the ISP also blocks incoming port 25, you then have not any
> choice and trying to run an MTA on that connection is wasted time. It
> can't ever be fully functional, too you will hurt your ISP's rules.

I don't think incoming port 25 is blocked anywhere, just outgoing (of
course, with outgoing blocked, it is hard to test incoming).  But I
don't really care about that.  I want incoming to come in on a
non-standard port to "bridge" the gap.  I'm not trying to hurt the
ISP's rules, just get back functionality that I wouldn't otherwise
have.

> > Jonathan
> 
> Alexander
> 

Jonathan