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Re: Complaint about change in spam controls of mailing lists @ RedHat

On 24 Apr 2003, Dr. Peter Boy wrote:

> Am Don, 2003-04-24 um 05.56 schrieb Tom Diehl:
> > I just got done configuring postfix to reject
> > mail that claims to be from the above domains but does not come from their
> > servers. I think this is a better way of rejecting spam without just dumping
> > mail from dialups. Unfortunately not everyone agrees with me.
> Tom, could you describe how you configured your postfix or post a link where 
> I can find information how to set it up? (I couldn't find sufficient information
> yet). 

Below is the message Wietse sent to the postfix-users list last year:

Date: Thu, 1 Aug 2002 11:21:45 -0400 (EDT)
From: Wietse Venema <wietse porcupine org>
Reply-To: Postfix users <postfix-users postfix org>
To: Postfix users <postfix-users postfix org>
Subject: Rejecting hotmail from non-hotmail sites etc.

Noel Jones:
> At 10:51 AM 8/1/02 -0400, Vivek Khera wrote:
> >What I do is block hotmail.com senders when the remote server's DNS
> >name is not within the hotmail.com domain.  Only occasionally does
> >this have a false positive: when someone uses, eg, Evite to send me an
> >invitation with a hotmail address, and when hotmail's DNS is hosed or
> >misconfigured for a while.
> >
> >I do the same for @yahoo.com, @msn.com, and @aol.com addresses as
> >well.
> care to share how you are doing this?

Either one uses a patch from Ron Guilmette, or one uses existing
Postfix features and some duct tape that does almost the same:
it stops mail from aol.com, hotmail.com etc. that does not come
from an aol.com, hotmail.com or legitimate forwarding site.

The result looks like this:

    Jul 31 00:31:59 spike postfix/smtpd[56456]: reject: RCPT from
        dyn-0.pat.lac00-nrp7.cha.dsl.cantv.net[]: 554
        <name-witheld yahoo com>: Sender address rejected: Mail must
        be sent from yahoo.com systems; from=<name-witheld yahoo com>
        to=<name-witheld wzv win tue nl>

Limitation: this will accept mail from user hotmail com that is
sent from an aol.com machine, but that is not a problem for me.

Configuration example below.


    smtpd_sender_restrictions =
        check_sender_access hash:/etc/postfix/spoof_sender_map
    smtpd_restriction_classes = match_client_domain
    match_client_domain =
        check_client_access hash:/etc/postfix/spoof_client_map
        check_sender_access regexp:/etc/postfix/strict_client.regexp

# List of domains that are often forged.
    aol.com   match_client_domain
    hotmail.com match_client_domain
    yahoo.com   match_client_domain

# The above domains, plus any sites that are legitimate mail forwarders.
    aol.com     OK
    hotmail.com OK
    yahoo.com   OK
    legitimate.forwarder.com OK

# Tell anyone else to bugger off.
    /@([^ ]+)$/ 554 Mail must be sent from $1 systems


.............Tom	"Nothing would please me more than being able to 
tdiehl rogueind com	hire ten programmers and deluge the hobby market 
			with good software." -- Bill Gates 1976

   			We are still waiting ....

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