File: //usr/share/webmin/postfix/help/opt_hash_queue_names.html
<header>Name of queue dirs split accross subdirs</header>
<center><tt>hash_queue_names</tt></center>
<hr>
This parameter specifies the names of queue directories that are split across
multiple subdirectory levels. Hashing MUST NOT be used with a world-writable
maildrop directory. Hashing MUST be used for the defer logfile directory, or
mail system performance will suffer.
<p>
Unfortunately, hashing the incoming or deferred queue can actually
slow the mail system down (<tt>mailq</tt> with an empty queue can take
several seconds) so it should be done only in case of emergency.
<hr>