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Old 06-12-2019, 07:13 AM   #1
Sisko1980
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Registered: Jun 2019
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Stop our Postfix from Sending Backscatter


Hello,

we have a Postfix-Mailserver set up, to send Mails from our Domains and receive Mails to our domains.

The problem is we receive mail like this:

Jun 11 05:21:32 server postfix/smtp[27122]: GA8A71A1: to=<someuser@ourdomain.com>, orig_to=<someadress@ourotherdomain.com>, relay=...:25, delay=19, delays=19/0.01/0.07/0, dsn=5.0.0, status=bounced (host ... said: 500 Syntax error, command unrecognized (in reply to MAIL FROM command))

with: from=<???JamesEdwards@somedomain.com>

Our server then sends a bounce mail to this forged from-address, to inform it of this error probably, but this user doesn't exist and we get then listed by Backscatterer, because we send bounces to non-existing users.

So, how can we prevent this? We could stop sending bounces altogether, but that doesn't seem like a sensible solution. Trying to verify the sender could itself lead to producing more spam. Anybody has a good solution in Postfix for that? Thanks in advance.
 
Old 06-12-2019, 08:04 AM   #2
scasey
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Registered: Feb 2013
Location: Tucson, AZ, USA
Distribution: CentOS 7.6
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You must send bounces when the condition for them occurs to be RFC compliant.
You should not send bounces when you receive a bounce, that is, when the MAIL FROM: is <> or postmaster

I can't help you with configuring postfix to do that, tho. Sorry.

I believe that'a what backscatterer.org is talking about, and they have instructions about how to use their RBL correctly on their site. They say they are blacklisting only 87101 IP addresses, which is nothing in the big scheme of things. I'm not sure why you care if you get listed there, even.
 
  


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