<header>DNS domains for blacklist lookups</header>

<center><tt>smtpd_client_restrictions: reject_rbl_client</tt></center>
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This parameter specifies an optional list of DNS domains that publish the
network addresses of blacklisted hosts.<br>
By default, RBL blacklist lookups are disabled. 
<p>
Specify a list of RBL domains, separated by commas.
<p>

The real-time blackhole list works as follows: reverse the client
network address, and reject service if it is listed below any of
the following domains.

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