Creating a "mail gateway"

[R.T.]

Stop re-inventing the wheel and use Google Apps For Your Domain (
https://www.google.com/a/ ).

Setup is about 5 seconds, and you get a load of useful tools in
addition to mail.



On Wed, Jun 11, 2008 at 3:08 PM, Ian Petersen <ispeters-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> Hi list,
>
> My father is stuck using Rogers as his ISP because the DSL connection
> is his area is terrible.  He runs a business from home and uses
> Exchange for his email server.  (He's somewhat married to Microsoft,
> despite 6 or 7 years of me trying to change his mind--Exchange isn't
> going anywhere anytime soon.)
>
> As was mentioned on this list, Rogers has recently made it a
> requirement that you log in to some web interface and add all your
> outgoing email addresses to some list before their relay will allow
> your email to pass.  My father is unwilling to use this interface on
> principle.  I told him we could probably make use of a virtual private
> server running Linux to get around Rogers' annoyances.  I imagined
> that he could rent something like a Slicehost machine, set up a VPN
> between home and the VPS, and then arrange his network such that mail
> comes and goes through the VPS, rather than through his Rogers IP.
>
> We went ahead and created a Slicehost account and it's configured with
> Debian Etch.  I've secured it as best I know how and intend to spend
> Fathers' Day making OpenVPN work on the Debian machine and on a
> machine at my father's house.  I realized, though, that my cursory
> understanding of TCP/IP routing might be getting in my way here.  I
> was expecting to configure his mail server to use the Debian machine
> as the default gateway (ie. the mail server would get to the internet
> by going across the VPN and out the Debian machine), and have the
> Debian machine port-forward the incoming mail port (25?) directly to
> his mail server.  I figured this would be a minimally-invasive change
> to his network settings and should "just work".  I realized, though,
> that it may not be so simple because whichever machine is running the
> OpenVPN connection needs to know to use the Rogers cable modem as the
> default gateway in order to get the tunneled packets out to the
> internet in the first place, and you can't have two default gateways.
>
> Can someone here suggest a solution?  What I'd like is for my father's
> DNS records to have the Debian machine's IP in their MX records, and
> for his Exchange server to be able to send and receive email through
> the Debian machine so he can ignore all of Rogers' nonsense.  As I
> mentioned in a previous post to this list, I have a copy of "Linux
> Networking Cookbook", so I think I'll be able to set up iptables to do
> whatever port-forwarding and routing is necessary, but I'm struggling
> with the overall network architecture.
>
> Thanks,
> Ian
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