engarde-users July 2002 archive
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engarde-users: [EnGarde] Re: Postfix - rejecting spoofed mail fr

[EnGarde] Re: Postfix - rejecting spoofed mail from:

From: Pete O'Hara <pete_at_nospam>
Date: Mon Jul 08 2002 - 18:28:21 GMT
To: engarde-users@engardelinux.org

Jeff Knox wrote:
> Basically, it should be able to block all outside mail claiming its from
> the local domain. Postfix should route any mail originating from the
> inside to the inside, without ever sending it to the outside anywhere, so
> it would know then that any mail comming from another mail server claiming
> to be from a domain it handles, is spam, should be fairly trivial. I
> believe thats what this guy wants, and actually I would like it too, i get
> a huge ammount of spam comming from fakenames@mydomains.com. In fact, my
> customers even call me on occation thinking their is a hacker or something
> on my system because of mail comming to them from their user names.
> Jeff
> fliphead.com

Try this:
in /etc/posfix create a file called "internal_domains" that looks like:

internal1.domain.com 554 You are an imposter! internal2.domain.com 554 You are an imposter!

postmap hash:/etc/postfix/internal_domains

then in main.cf in your "smtp_recipient_restrictions" after the "permit_mynetworks" and BEFORE "check_relay_domains" add "check_sender_access hash:/etc/postfix/internal_domains"

and run "postfix reload"

This should reject the mail attempt with the message "You are an imposter!" after checking internal machines in $mynetworks.


Pete O'Hara
Systems Engineer
Guardian Digital, Inc.

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