Vasya Pupkin:
> Hello.
>
> First, I have spent two days reading articles and searching web for
> solution but failed there. I am using postfix as an mx for my domains,
> it accpets mail for different addresses withing my domains which is
> then forwarded to other external domains, i.e. google.com and other
> mail services. Mail for unknown users is rejected, many other check
> are performed, but still sometimes my system acts as a backscatterer
> when something like this happens:
>
> 1. Incoming mail passes all tests, it's coming to one of the addresses
> within my domain, i.e. existing-u...@mydomain.tld
> 2. Postfix then forwards mail to external domain, i.e. myem...@mailservice.tld
> 3. For some reason mailservice.tld rejects this mail, i.e. it doesn't
> like it's content or size.
> 4. Postfix then bounces mail to sender, which can be forged, and thus,
> becoming a backscatterer.
>
> Is there any way to prevent postfix from sending bounces anywhere?
The best conutermeasure is not to forward spam.
The second-best solution requires the ability to predict if a
specific message will be rejected down-stream. Let me know when
you solve that, so I can add it to Postfix.
Wietse
