Re: Postfix filtering for Exchange server

[Travis Owens <openbook@linuxmds.com>]

Steve,

Thanks for your help! It worked out great! Approximately a 70% reduction
in spam, before the regexp-s are setup.

Thanks a ton!
Travis

On Thu, 2004-05-20 at 20:35, Steven Pritchard wrote:
> On Thu, May 20, 2004 at 05:30:26PM -0500, Travis Owens wrote:
> > I'm looking to setup a postfix server on a firewall/router to filter
> > emails -- blocking spam -- then relaying it to the MS Exchange server on
> > the LAN.
> > 
> > First, does this make sense, and is it plausible? (I'm pretty sure it
> > is)
> 
> Yes, and yes.
> 
> > I believe if I use the relay_domains parameter with the
> > relay_recipients_maps setup for all the valid addresses listed, along
> > with the Exchange server setup with a higher priority in the DNS records
> > for internal resolution, the firewall/postfix server will accept the
> > mail via postfix and filter via the rules that I establish, then pass
> > the valid emails on to the Exchange server.
> 
> I don't think you want to do this via DNS.  You should let postfix
> route everything based on explicit rules.
> 
> > Here's the basic setup in case I'm having trouble explaining in an
> > understandable format:
> > 
> > Postfix:	rt1.domain.com 		10.0.0.254
> > Exchange:	ntmain.domain.com	10.0.0.2
> > 
> > DNS records = rt1 = priority 10, while ntmain = priority 5
> > 
> > INET -> Postfix (10.0.0.254) -> Win2K (10.0.0.2)
> 
> What you really want to do is not even list ntmain as an MX.  You want
> all incoming traffic to hit rt1, and on that box you want the
> following:
> 
> /etc/postfix/main.cf:
> 
>   mydestination = $myhostname, localhost.$mydomain, localhost,
>                   /etc/postfix/local-host-names
> 
>   transport_maps = hash:/etc/postfix/transport
> 
> /etc/postfix/local-host-names:
> 
>   domain.com
>   ntmain.domain.com
> 
> /etc/postfix/transport:
> 
>   domain.com		smtp:[ntmain.domain.com]:25
>   ntmain.domain.com	smtp:[ntmain.domain.com]:25
> 
> Make sure you do "postmap /etc/postfix/transport".
> 
> Oh, and if you happen to be running Fedora/Red Hat, I have packages
> for amavis, and I would be happy to give you the other few steps that
> it takes to set that up so you can easily use it for all the
> spam/virus filtering...
> 
> Steve
-- 
Travis Owens <openbook@linuxmds.com>


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