From: ram (ramnetcore.co.in)
Date: Mon Aug 04 2008 - 09:03:48 CDT

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On Mon, 2008-08-04 at 10:56 +0200, lists.postfix-usersduinheks.nl
wrote:
> Hallo ram,
>
> Op vrijdag 01 augustus 2008 schreef ram aan lists.postfix-usersduinheks.nl:
>
> >> Occasionally external systems are tying to send mail with a
> >> faked sender address via my system. So far no harm is done,
> >> ad they have not been able to create a real user name. But
> >> I would like to stop them before they use my mail system,
> >> as soon as they make contact. How can I do this?
> ra> I dont see any reason for you to worry. You are doing a
> ra> reject_unauth_destination already
>
> It's not the destination I'm worried about, it's the sender.
> There is a [small] possibility that the culprit guesses a real
> user name on my system and then sends spam or other unpleasant
> things across the world. I would not like that...
>
Enable smtp authentication. Allow only authenticated users of your
domain to send to outside world. A spammer can guess the username but
cant get the password
( I am assuming you dont allow the "username=password" on your
machine :-) )

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