kyle-qmail at memoryhole
Apr 21, 2008, 8:37 AM
Post #2 of 3
(475 views)
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On Monday, April 21 at 08:49 AM, quoth Oliver Welter:
> My qmail server hosts the domains xyz.com, the address info[at]xyz.com
> is forwarded to a domain at another provider.
> A mail with a senders address of the GMX Mailservice hit this alias, and
> was forwarded to the other provider. The mail was rejected by them,
> because the gmx.net domain uses SPF and I am obviously not an allowed
> origin for it.
The GMX Mailservice has decided to attempt to prevent you from
forwarding their email, and you are asking for some ideas for
circumventing their policy?
Ummm, okay. As long as you're aware of what you're doing.
Why is thwarting GMX so urgent?
> I know that this is a protocol immanent problem which was often
> discussed, but I now urgently need some sort of workaround (Sender
> rewriting?).
The easiest technique is to simply RESEND the message, with your own
server as the sender. To do so, you would simply put this in your
.qmail file:
|env NEWSENDER=postmaster[at]xyz.com forward $RECIPIENT
When you do so, you are taking responsibility for handling all bounces
(i.e. if $RECIPIENT doesn't exist) and you're claiming responsibility
for any and all spam that goes through that forward. This is
essentially equivalent to SPF sender rewriting, with the exception
that the "real" sender isn't being encoded in the sender address.
If you wish to encode the "real" sender in the new sender's address,
you can try something like this:
|env NEWSENDER=info-`echo $SENDER|sed 's/@/=/g'`@xyz.com forward $RECIPIENT
Now, this solution is *VERY* naive, and is generally a bad solution
for many reasons. Then again, so is SPF sender rewriting (SRS). Before
you go very far down this path, there are two web pages you need to
read and fully consider:
http://homepages.tesco.net/J.deBoynePollard/FGA/smtp-spf-is-harmful.html
http://ghewgill.livejournal.com/83857.html
~Kyle
--
The search for the truth is the noblest occupation of man. Its
publication is a duty.
-- Anne Louise Germaine de Stael
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