Re: email problems

At 10:26 AM 10/27/2004, paddy wrote:
>On Wed, Oct 27, 2004 at 08:01:29AM -0700, Ralf Quint wrote:
> > At 07:17 AM 10/27/2004, Martin Pot wrote:
> > >On Wed, 27 Oct 2004, SENDHERE wrote:
> > >
> > >> hello.. wondering do i have to open a service port for out going
> > >> sendmail on linux servers??????
> > >
> > >No, as Smoothwall doesn't block any outbound traffic by default.
> > Don't know if either Martin or me is probably misunderstanding your
> > question, but for email "servers" to properly communicate with other email
> > servers on the Internet via SMTP<,you have of course to forward TCP/25 
> from
> > all source IP's to your email server, no matter if sending or receiving...
>
>He does explicitly state outgoing.  Smoothwall NATs on all ports outbound, ie:
>no you don't need to open a port.  You would only need to set up the NAT in
>the other direction to accept incoming connections.  It is fairly ordinary
>to have working internet email using only outbound connections - polling with
>something like pop3 or esmtp for incoming mail.  However, of course, you are
>right that forwarding port(s) would be necessary to take incoming connections,
>to receive mail 'internet-style'.  I wouldn't be in a hurry to recommend that
>to anyone asking this question.

The catch with email (talking SMTP here!) is that SMTP is a two-way 
communication. It requires both incoming and outgoing connections on the 
same port, TCP/25...

If you run a real email "server", and for most proxies, this means that you 
have in fact forward TCP/25 to your server, otherwise, the remote email 
server isn't able to "talk back" and your email won't get delivered...

Ralf
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