Я Outlook\\\\\\\\\\\\\\\'ом не пользуюсь, поэтому проверить не могу, но попробуйте заменить:
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;$from=\\\\\\\\\\\\\\\'test@test.ru\\\\\\\\\\\\\\\';
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;mail($to, $_POST[\\\\\\\\\\\\\\\'title\\\\\\\\\\\\\\\'], $mess, \\\\\\\\&amp;amp;amp;quot;From:\\\\\\\\&amp;amp;amp;quot;.$from);
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;на
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;$from=\\\\\\\\\\\\\\\'test@test.ru\\\\\\\\\\\\\\\';
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;$headers = \\\\\\\\\\\\\\\'From: \\\\\\\\\\\\\\\'.$from . \\\\\\\\&amp;amp;amp;quot;\\\\\\\\\\\\\\\\r\\\\\\\\\\\\\\\\n\\\\\\\\&amp;amp;amp;quot; .
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;\\\\\\\\\\\\\\\'Content-type: text/plain; charset=\\\\\\\\&amp;amp;amp;quot;windows-1251\\\\\\\\&amp;amp;amp;quot;\\\\\\\\\\\\\\\' . \\\\\\\\&amp;amp;amp;quot;\\\\\\\\\\\\\\\\r\\\\\\\\\\\\\\\\n\\\\\\\\&amp;amp;amp;quot;;
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;mail($to, $_POST[\\\\\\\\\\\\\\\'title\\\\\\\\\\\\\\\'], $mess, $headers);
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;====================
<br>&lt;br&gt;&amp;lt;br&amp;gt;&amp;amp;lt;br&amp;amp;gt;НЕ РАБОТАЕТ