Re: mail forwarding loop :: SPAM

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mail forwarding loop :: SPAM
\ Scott Ruckh (21 Jan 2008)
. \ Justin Piszcz (21 Jan 2008)
. \ (Wietse Venema) (21 Jan 2008)
. . \ Scott Ruckh (21 Jan 2008)

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Subject:	Re: mail forwarding loop :: SPAM
Group:	Postfix-users
From:	Scott Ruckh
Date:	21 Jan 2008

> Scott Ruckh:
>> I searched the archives for mail forwarding loops and come across quite a
>> few articles discussing .forward files, and other messages talking about
>> Delivered-To: field being changed in envelope header, but I was not sure
>> if I have the same issue and if there was a solution.
>
> There are envelopes (sender and receiver addresses in SMTP commands),
> and headers (the information at the start of the email message), but
> there is no such thing as an envelope header.
>
>> So I have some clown sending email from 87.88.14.31. The From: field
>> contains an invalid email address from my domain. The Delivered-To:
>> field
>> contains my address.
>>
>> I end up with a "mail forwarding loop for <my email address>" email from
>> MAILER-DAEMON.
>>
>> As email accounts are separate from system machine accounts this is not
>> an
>> issue with a .forward file. This sounds like an issue with then
>> Delivered-To: field being injected with bad info.
>>
>> I did not find a resolution to this issue. What can I do to block these
>> types of emails?
>
> The simple solution has been discussed many times: disable the
> Postfix tests for Delivered-To: headers.
>
> A more sophisticated solution would detect programmatically the
> difference between a forwarding loop and a false Delivered-To:
> header (presumably by examining Received: header information). A
> simple test would just count the number of pre-existing Received:
> headers. A forwarding loop needs at least two.
>
> Wietse

Thanks for the replies. I will have to investigate a bit more.