[NBLUG/talk] Hosts file and spam filtering
omar at omnicode.com
Wed Apr 22 10:12:11 PDT 2015
Anybody an expert on DNS and Postfix spam filtering? My problem is that
I use smtpd_client_restrictions check_reverse_client_hostname to check
for senders that don't have a reverse client host name. It blocks an
average of about 3,000 potential spam requests per day, so I consider it
The problem is that there are a few admins who refuse to configure their
mail servers properly, so I'm left trying to create a white list for
these few senders.
The easiest way I thought of doing the white list is to use the
/etc/hosts file to kluge in a reverse lookup. I've seen docs that talk
about reverse lookups in hosts files. However, I'm having a more basic
problem. I try to enter something like:
Then use the command:
The result comes back as a non-existent domain.
This is Centos 6.6. I'm in the process of switching to Ubuntu, but that
hasn't happened yet.
Am I missing something with the /etc/hosts file and using the host command?
I know that I can use a DNS server as well. I'd like to try to avoid
that because I only want the mail server to use that reverse lookup.
Also there are other Postfix solutions, but they all seem complex.
Worst case is that I have a custom Milter that can do the reverse
lookups itself. I'd rather use the stock Postfix solution, though.
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