full-disclosure - Re: Strange from address

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From: szalkai at 2fkft.com (Akos Szalkai)
Subject: Re: Strange from address

Hi James,

> If you insert the following string into the mail from: field #@[] it
> appears to by pass the mx check and replys ok.

if you read the qmail manpages (addresses(5) specifically), you can see
that this a qmail extension: this is the envelope sender of a double
bounce.

What I fail to see however, is that how it can be a security problem.
It is not very difficult to generate envelope senders that pass your mx
check anyway.

Regards,
Akos

-- 
Akos Szalkai <szalkai@...hu>
IT Consultant, CISA
2F 2000 Szamitastechnikai es Szolgaltato Kft.
Tel: (+36-1)-4887700  Fax: (+36-1)-4887709  WWW: http://www.2f.hu/