[feldon23]

The simplest form, blocking users with 0 posts from sending PMs, can be accomplished by inserting this at the top:

<if condition="$bbuserinfo[posts] < 1">
  <table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
    <tr>
      <td class="tcat">Send a Private Message</td>
    </tr>

  <tr>
    <td class="panelsurround" align="center">
      <div class="panel">
<p><b>Because of concerns with unsolicited e-mail, we are now asking that visitors to our forums participate in our forum before sending private messages.</b><br /><br />
Please introduce yourself and tell us a little bit about yourself before sending private messages to other members.</p>
      </div>
    </td>
  </tr>
<else />

and this at the bottom:

</if>

of the pm_newpm template.