Date: Mon, 28 Apr 1997 14:31:01 -0400 (EDT) From: "David H. Brierley" <dave@galaxia.com> To: freebsd-isp@FreeBSD.org Subject: Re: SMTP gateway clients Message-ID: <Pine.BSF.3.95.970428141252.2711A-100000@terminus> In-Reply-To: <Pine.BSF.3.91.970428090307.10264p-100000@panda.hilink.com.au>
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> > It's called ETRN.
> > telnet to port 25 and enter the command
> >
> > ETRN domain.name
> > QUIT
>
> but it only works with a fixed IP address for the relay. The original
> question was how to use dynamic IP address for the relay.
What I did was to write a short program that would modify the
sendmail configuration files to reflect the "current" IP address
for the domain. Create a special login/password combination which
runs the program, have the program prompt for a domain name and a
second password, query the system to find the IP address of the
incoming connection, rewrite the files. When the customer then
connects a few seconds later and gives the "ETRN" comand it will
deliver the mail just fine. The biggest problem is making sure
that the host at IP address x.y.z.z is still the same host 5 minutes
later, otherwise you end up delivering the mail to the wrong machine.
This is probably best handled by having the original program maintain
some form of connection to the customers machine and reset the
sendmail configuration files when the connection drops.
Before anybody asks, I no longer work for the ISP that I did all
of this for so I no longer have access to the code. On the other
hand, if anybody wants to hire me to come up with a solution for
them I am available at reasonable rates.
--
David H. Brierley
UNIX System Consultant
dave@galaxia.com
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