$re = '/[^<>\s](?![^<>]*>)/m';
$str = 'sd<p><em>Hi [User</em></p>
<p><em>Tack för visat intresse.</em></p>
<p><em>Good luck!</em><em> </em></p>
<p><em>Sincerely</em></p>sd';
$subst = "n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php