On Mon, Nov 16, 2009 at 12:53:14PM -0700, Jim Lang wrote:
> OK here is the scenario.
> Spammer sends mail to: u...@myclientsdomain.com from forged address
> vic...@randomdomain.com
>
> If u...@myclientsdomain.com is delivered locally, not a problem, if the
> address is invalid, postix rejects the mail during the smtp connection.
>
> But if u...@myclientsdomain.com is an alias to mycli...@otherserver.com,
> postfix accepts the mail as deliverable and forwards it to hotmail.com.
> But if mycli...@otherserver.com can for whatever reason not be delivered,
> otherserver.com does what it is supposed to do and rejects the mail during
> the smtp connection, which causes postfix to send out a non-delivery
> report to vic...@randomdomain.com -- backscatter.
>
> Is there a way to stop this?
Some backscatter is unavoidable, you can keep the volume low by removing
local aliases to no-longer-valid external addresses, and by rejecting
mail from spam sources, using good blacklists, ...
--
Viktor.
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