Reverse address entries
Barry Margolin
barmar at alum.mit.edu
Tue Jul 2 15:32:19 UTC 2013
In article <mailman.737.1372773227.20661.bind-users at lists.isc.org>,
Daniel McDonald <dan.mcdonald at austinenergy.com> wrote:
> The other place reverse DNS is routinely queried is SMTP. If you care
> enough to send mail, you should care enough to set up your reverse entries
> realistically so that spam filters will recognize that you are trying to
> actively manage your email server and this isn't mail from a BOT...
Reverse DNS is generally necessary, but may not be sufficient. Your IP
also has to NOT be on one of the many block lists. These lists are
populated with IPs that have spamming history, as well as IPs that ISPs
have volunteered as being used for residential services rather than
commercial users.
I suppose it's obvious, but the other general place where reverse DNS is
important is if you make use of hostnames or domain suffixes in filter
files like hosts.allow and hosts.deny. If your hosts.allow file contains
something like:
sshd: *.yourdomain.com
then the server will do a reverse lookup and forward validity check
before testing whether the hostname ends in .yourdomain.com.
--
Barry Margolin
Arlington, MA
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