File: //usr/share/webmin/postfix/help/opt_local_recipient_maps.html
<header>Reject unknown local users</header>
<center><tt>local_recipient_maps</tt></center>
<hr>
This parameter specifies optional lookup tables with all users that are local
with respect to <tt>$mydestination</tt> ("what domains to receive mail
for")and <tt>$inet_interfaces</tt> ("network interfaces for receiving
mail") . If this parameter is defined, then the SMTP server will reject
mail for unknown local users.
<p>
Put tables with bare usernames such as <tt>unix:passwd.byname</tt> and alias
maps. Example: <tt>$alias_maps unix:passwd.byname</tt>.
<p>
Beware: if the Postfix SMTP server runs chrooted, you may have to
copy the passwd database into the jail. This is system dependent.
<hr>